CefSharedProcessMessageBuilder supports creation of a CefProcessMessage
backed by a CefSharedMemoryRegion.
Performance tests comparing the existing ArgumentList approach and the new
SharedMemoryRegion approach have been added to cefclient at
http://tests/ipc_performance.
CefMessageRouter has been updated to use SharedMemoryRegion as transport
for larger message payloads. The threshold is configurable via
|CefMessageRouterConfig.message_size_threshold|.
To test:
run `ceftests --gtest_filter=SendSharedProcessMessageTest.*:SharedProcessMessageTest.*:MessageRouterTest.Threshold*`
All file dialogs irrespective of source, platform and runtime will now be
routed through CefFileDialogManager and trigger CefDialogHandler callbacks
(see issue #3293).
Adds Chrome runtime support for CefBrowserHost::RunFileDialog and
CefDialogHandler callbacks.
Adds Alloy runtime support for internal GTK file and print dialogs on Linux
subject to the following limitations:
1. Internal GTK implementation:
- Cannot be used with multi-threaded-message-loop because Chromium's
internal GTK implementation is not thread-safe (does not use GDK threads).
- Dialogs will not be modal to application windows when used with off-screen
rendering due to lack of access to the client's top-level GtkWindow.
2. Cefclient CefDialogHandler implementation:
- Cannot be used with Views because it requires a top-level GtkWindow.
Due to the above limitations no dialog implementation is currently provided for
Views + multi-threaded-message-loop on Linux. In cases where both
implementations are supported the cefclient version is now behind an optional
`--use-client-dialogs` command-line flag.
Expressly forbids multiple simultaneous file dialogs with the internal platform
implementation which uses modal dialogs. CefDialogHandler will still be notified
and can optionally handle each request without a modal dialog (see issue #3154).
Removes some RunFileDialog parameters that are not supported by the Chrome file
dialog implementation (selected_accept_filter parameter, cef_file_dialog_mode_t
overwrite/read-only flags).
Calling DetachToUserFree() on a CefString holding a reference should copy the
value instead of transferring ownership.
A new `StringTest.Ownership` test has been added for this behavior.
This change provides a generic solution for active (key) window tracking that
works with both Views-hosted and native windows on MacOS. With this new approach
we can now successfully route top menu actions to the currently active window.
Prior to this change CEF's Views API was using focus notifications as a proxy
for window activation notifications. That doesn't work on MacOS where NSWindow
activation (key status) is independent of NSView focus (first responder) status,
and changes in activation don't necessarily generate focus notifications (see
NativeWidgetMac::OnWindowKeyStatusChanged). To make this work reliably on all
platforms we now expose a CefWindowDelegate::OnWindowActivationChanged callback.
This change also fixes an uninitialized variable
(RootWindowMacImpl::with_extension_) that was causing flaky behavior in
RootWindowManager::OnRootWindowActivated.
To test:
1. Run `cefclient [--use-views]`
2. Select Popup Window from the Tests menu. Do not explicitly activate the popup
window (e.g. don't click on it).
3. Verify that further Tests menu actions go to the popup window.
4. Change activation to a first window by clicking on it. Verify that Test
menu actions go to that window.
5. Close the currently active window. Do not explicitly activate the remaining
window (e.g. don't click on it).
6. Verify that Test menu actions go to the only remaining window.
Popup windows will be created on the display that best matches the requested
coordinates. The requested size will apply to the content area (as required by
JS documentation) and window size will be reduced if necessary to fit within the
target display. The requested origin will apply to the window (including frame)
and will be modified if necessary so that the window is fully visible on the
target display.
This change adds a `--use-default-popup` command-line option to cefclient. When
specified, popup windows will be created with default styling (e.g. without an
application-provided native parent window).
This change also adds some reasonable default window bounds in cases where they
are not specified by the client.
This change adds Chrome runtime support on Windows and Linux for creating a
browser parented to a native window supplied by the client application.
Expected API usage and window behavior is similar to what already exists with
the Alloy runtime. The parent window handle should be specified by using
CefWindowInfo::SetAsChild in combination with the CefBrowserHost::CreateBrowser
and CefLifeSpanHandler::OnBeforePopup callbacks.
The previously existing behavior of creating a fully-featured Chrome browser
window when empty CefWindowInfo is used with CreateBrowser remains unchanged
and Views is still the preferred API for creating top-level Chrome windows
with custom styling (e.g. title bar only, frameless, etc).
The cefclient Popup Window test with a native parent window continues to crash
on Linux with both the Alloy and Chrome runtimes (see issue #3165).
Also adds Chrome runtime support for CefDisplayHandler::OnCursorChange.
To test:
- Run `cefclient --enable-chrome-runtime [--use-views]` for the default (and
previously existing) Views-based behavior.
- Run `cefclient --enable-chrome-runtime --use-native` for the new native
parent window behavior.
- Run `cefclient --enable-chrome-runtime --use-native --no-activate` and the
window will not be activated (take input focus) on launch (Windows only).
- Run `cefclient --enable-chrome-runtime [--use-views|--use-native]
--mouse-cursor-change-disabled` and the mouse cursor will not change on
mouseover of DOM elements.
With same-site BFCache enabled every navigation can now potentially be served
via the BFCache. To support this internally a new top-level RenderFrame object
may be created for each new navigation. As a result, OnBrowserCreated may now
be called multiple times with the same browser ID in a given renderer process
(a behavior previously only seen with cross-site navigations and different
renderer processes).
BFCache navigations do not trigger the same Chromium notifications as a normal
load. To avoid breaking CEF API usage expectations we now synthetically
generate the load-related callbacks that would otherwise be missing
(OnLoadingStateChange with isLoading=true, OnLoadStart, OnLoadEnd). The
|httpStatusCode| argument to OnLoadEnd will be 0 in this case.
To test:
- Run `FrameHandlerTest.*:MessageRouterTest.*:NavigationTest.*`
- Run `NavigationTest.LoadSameOriginLoadURL` for OnBrowserCreated behavior.
- Run `NavigationTest.History` for load-related callback behavior.
This change adds a CefDownloadHandler::CanDownload callback for optionally
blocking user-initiated downloads (e.g. alt + link click or link click that
returns a `Content-Disposition: attachment` response from the server).
To test:
- Run `ceftests --gtest_filter=DownloadTest.*`.
- Run `cefclient --hide-controls`. User-initiated downloads will be blocked.
This change adds a CefCommandHandler::OnChromeCommand callback for optionally
handling Chrome commands triggered via menus or keyboard shortcuts. Supported
command IDs are listed in a new cef_command_ids.h header file.
To test: Run `cefclient --enable-chrome-runtime --hide-controls`. Most commands
will blocked and removed from context menus.
This change adds `CefBrowserSettings.chrome_status_bubble` for controlling
whether the Chrome status bubble will be used.
Testable in cefclient by passing the `--hide-chrome-status-bubble`
command-line flag.
This functionality stopped being relevant after the removal of Flash support
in January 2021. The last remaining PPAPI plugin (PDF viewer) will switch to
a non-plugin implementation (PdfUnseasoned) in M100.
With PdfUnseasoned the PDF file will be loaded in a dedicated renderer process.
We identify this process by adding the kPdfRenderer command-line flag (similar
to how kExtensionProcess is used to identify an extension renderer process). We
then avoid calling GetNewBrowserInfo for the PDF renderer process because we
know the request will otherwise time out.
We need to override ChromeMimeHandlerViewGuestDelegate to handle
OnGuestAttached/Detached callbacks in order to account for the guest renderer
process hosting the PDF extension.
Additional work will be required to account for the renderer process hosting the
PDF viewer when using `--enable-features=PdfUnseasoned` (see issue #2969).
- Remove CefRequestContextHandler::OnBeforePluginLoad and
CefRequestContext::PurgePluginListCache (fixes issue #3047). These methods
stopped being relevant after the removal of Flash support in January 2021.
The last remaining PPAPI plugin (PDF viewer) will switch to a non-plugin
implementation in the near future (see https://crbug.com/702993#c58) and
functionality related to plugin filtering has already been removed in
https://crrev.com/343ae351c9.
When BackForwardCache is enabled and the user navigates the main frame
back/forward a new RFH may be created for an existing main frame GlobalId value
and CefFrameHostImpl (e.g. an object that was previously Detach()ed after main
frame navigation called SetMainFrame, but for which RenderFrameDeleted was not
subsequently called due to insertion in the BackForwardCache). In this case we
can re-attach the new RFH to the existing main frame CefFrameHostImpl in
RenderFrameHostStateChanged and resume processing of messages.
Swapping back/forward to an existing (already loaded) renderer does not trigger
new notifications for draggable regions (e.g. RenderFrameObserver::
DraggableRegionsChanged is not called by default). We therefore explicitly
request an update of draggable regions by sending the DidStopLoading message to
the renderer.
A new |reattached| parameter is added to CefFrameHandler::OnFrameAttached to
support identification of BackForwardCache usage by the client.
To test with unit tests:
Run `ceftests --gtest_filter=DraggableRegionsTest.DraggableRegionsCrossOrigin
--enable-features=BackForwardCache`
To test manually:
1. Run `cefclient --enable-features=BackForwardCache --use-views
--url=http://tests/draggable`, note that draggable regions work.
2. Load https://www.google.com via the address bar, note that draggable regions
are removed.
3. Go back to http://tests/draggable, note that draggable regions work.
4. Go forward to https://www.google.com, note that draggable regions are
removed.
To test:
Run `cefclient.exe --use-views --hide-frame --hide-controls`
Add `--enable-chrome-runtime` for the same behavior using the Chrome location
bar instead of a text field.
Widevine CDM binaries will be downloaded on supported platforms shortly after
application startup. Widevine support will then become available within a few
seconds after successful installation on Windows or after the next application
restart on other platforms. The CDM files will be downloaded to a "WidevineCdm"
directory inside the `CefSettings.user_data_path` directory.
Pass the `--disable-component-update` command-line flag to disable Widevine
download and installation. Pass the `--component-updater=fast-update` command-
line flag to force Widevine download immediately after application startup.
See the related issue for additional usage details.
When BackForwardCache is enabled the old RFH tree may be cached instead of being
immediately deleted as a result of main frame navigation. If a RFH is cached
then delivery of the CefFrameHandler::OnFrameDetached callback will be delayed
until the the RFH is ejected from the cache (possibly not occurring until the
browser is destroyed). This change in OnFrameDetached timing was causing
FrameHandlerTest.OrderSubCrossOrigin* to fail, and the inclusion of cached
frames in CefBrowserInfo::GetAllFrames was causing
FrameTest.NestedIframesDiffOrigin to fail.
BackForwardCache is currently being tested via field trials (see
https://crbug.com/1171298) and can be explicitly disabled using the
`--disable-back-forward-cache` or `--disable-features=BackForwardCache`
command-line flags.
Automatically report unit tests to the TeamCity server if run within TeamCity.
See tests/gtest/teamcity/README.cef for details.
To test: Set the TEAMCITY_PROJECT_NAME environment variable and run ceftests.
Fixes the following error:
[FATAL:cef_bind_internal.h(868)] Check failed: receiver->HasAtLeastOneRef().
base::Bind{Once,Repeating}() refuses to create the first reference to ref-counted
objects. That typically happens around PostTask() in their constructor, and such
objects can be destroyed before `new` returns if the task resolves fast enough.
- Convert scoped_ptr to std::unique_ptr from <memory>
- Convert arraysize to base::size from include/base/cef_cxx17_backports.h
- Convert NULL to nullptr
- Include include/base/cef_callback.h instead of include/base/cef_bind.h
- Implicit conversion of CefRefPtr<T> or scoped_refptr<T> to T* is gone;
use .get() instead
See the issue for additional details.
ClientAppRenderer::Delegate callbacks are executed for all tests. In this case
CorsTest.IframeAllowScriptsCustomNonStandardSchemeToServer was crashing on Linux
because CefBrowser::GetMainFrame() returns nullptr in the renderer process when
called from a cross-origin sub-frame.
The AbortAfterCreated and AbortBeforeBrowse tests were flaking due to a race
between request handling and browser close. The tests would fail if the request
handling completed first.
See the new cef_frame_handler.h for complete usage documentation.
This change includes the following related enhancements:
- The newly added CefBrowser::IsValid method will return false (in the browser
process) after CefLifeSpanHandler::OnBeforeClose is called.
- CefBrowser::GetMainFrame will return a valid object (in the browser process)
until after CefLifeSpanHandler::OnBeforeClose is called.
- The main frame object will change during cross-origin navigation or
re-navigation after renderer process termination. During that time,
GetMainFrame will return the new/pending frame (in the browser process) and
any messages that arrive for the new/pending frame will be correctly
attributed in OnProcessMessageReceived.
- Commands to be executed in the renderer process that may fail during early
frame initialization (ExecuteJavaScript, LoadRequest, etc.) will now be
queued until after the JavaScript context for the frame has been created.
- Logging has been added for any commands that are dropped because they arrived
after frame detachment.
This change introduces a few minor CEF API behavior changes:
- A CefProcessMessage object cannot be reused after being passed to
SendProcessMessage.
- The |extra_info| argument to CefRenderProcessHandler::OnBrowserCreated may
now be NULL.
Where appropriate, we now utilize the default UTF string encoding format and
shared memory to reduce copies and conversions for the cross-process
transfer of arbitrary-length strings. For example, CefFrame::GetSource/GetText
now involves zero UTF conversions and zero copies in the browser process for
the CefString delivered to CefStringVisitor::Visit().
This change adds support for CEF settings configuration of accept_language_list.
If specified, this value will take precedence over the "intl.accept_languages"
preference which is controlled by chrome://settings/languages.
With the Chrome runtime, Profile initialization may be asynchronous. Code that
waited on CefBrowserContext creation now needs to wait on CefBrowserContext
initialization instead.
The policy->CanAccessDataForOrigin CHECK in NavigationRequest::
GetOriginForURLLoaderFactory was failing because unregistered schemes
(which are already considered non-standard schemes) didn't trigger the
registered non-standard scheme allowance that we previously added in
ChildProcessSecurityPolicyImpl::CanAccessDataForOrigin. This change
modifies GetOriginForURLLoaderFactory to always return an opaque/unique
origin for non-standard schemes resulting in unregistered and non-standard
schemes receiving the same treatment.
New test coverage has been added for this condition, and can be run with:
ceftests --gtest_filter=CorsTest.*CustomUnregistered*
The Chrome runtime requires that cookieable scheme information be available
at Profile initialization time because it also triggers NetworkContext creation
at the same time. To make this possible, and to avoid various race conditions
when setting state, the cookieable scheme configuration has been added as
|cookieable_schemes_list| and |cookieable_schemes_exclude_defaults| in
CefSettings and CefBrowserContextSettings. The CefCookieManager::
SetSupportedSchemes and CefBrowserProcessHandler::GetCookieableSchemes methods
are no longer required and have been removed.
This change also modifies chrome to delay OffTheRecordProfileImpl initialization
so that |ChromeBrowserContext::profile_| can be set before
ChromeContentBrowserClientCef::ConfigureNetworkContextParams calls
CefBrowserContext::FromBrowserContext to retrieve the ChromeBrowserContext
and associated cookieable scheme information. Otherwise, the
ChromeBrowserContext will not be matched and the NetworkContext will not be
configured correctly.
The CookieTest suite now passes with the Chrome runtime enabled.
GTK3 is required by the Chrome runtime. The cefclient off-screen rendering
example no longer works with Ubuntu 16.04. With end-of-life in April 2021
we are dropping support for 16.04 in the near future in any case.
The Chrome browser can now be hosted in a Views-based application on Mac
(see issue #2969).
To launch a fully-featured Chrome window using cefsimple:
$ open cefsimple.app --args --enable-chrome-runtime
To launch a minimally-styled Views-hosted window using cefsimple:
$ open cefsimple.app --args --use-views [--enable-chrome-runtime]
To launch a fully-styled Views-hosted window using cefclient:
$ open cefclient.app --args --use-views [--enable-chrome-runtime]
Known issues:
- Some Views unit tests are currently failing on Mac.
The Chrome browser can now be hosted in a Views-based application on Windows
and Linux.
To launch a fully-featured Chrome window using cefsimple:
$ cefsimple --enable-chrome-runtime
To launch a minimally-styled Views-hosted window using cefsimple:
$ cefsimple --enable-chrome-runtime --use-views
To launch a fully-styled Views-hosted window using cefclient:
$ cefclient --enable-chrome-runtime --use-views
Views unit tests also now pass with the Chrome runtime enabled:
$ ceftests --gtest_filter=Views* --enable-chrome-runtime
Known issues:
- Popup browsers cannot be intercepted and reparented.
- Only install network intercepts for Profiles that have an associated
CefBrowserContext. For incognito windows the CefBrowserContext is
associated with the OffTheRecordProfileImpl's original Profile.
- cefsimple: Return the default CefClient instance for browser windows
created via the Chrome UI, and allow Chrome to show error pages.
Switch to using g_main_context_default() in MainMessageLoopMultithreadedGtk. As of M86
(https://crrev.com/b960daf4e6) Chromium now creates its own context in MessagePumpGlib so
we can use the default context in cefclient. This is also more "correct" from a GTK usage
perspective. As part of this change all GTK dialogs and callbacks are now executed on the
main thread instead of the UI thread (note that these are the same thread when not using
multi-threaded-message-loop).
The cursor change can now be handled by the client with both windowed and
off-screen rendering.
Returning true from OnCursorChange will disable the default cursor change
behavior. This is functionally equivalent to the
CefBrowserHost::SetMouseCursorChangeDisabled method, so that method has been
removed.
This change adds support for:
- Protocol and request handling.
- Loading and navigation events.
- Display and focus events.
- Mouse/keyboard events.
- Popup browsers.
- Callbacks in the renderer process.
- Misc. functionality required for ceftests.
This change also adds a new CefBrowserProcessHandler::GetCookieableSchemes
callback for configuring global state that will be applied to all
CefCookieManagers by default. This global callback is currently required by the
chrome runtime because the primary ProfileImpl is created via
ChromeBrowserMainParts::PreMainMessageLoopRun (CreatePrimaryProfile) before
OnContextCreated can be called.
ProfileImpl will use the "C:\Users\[user]\AppData\Local\CEF\User Data\Default"
directory by default (on Windows). Cookies may persist in this directory when
running ceftests and may need to be manually deleted if those tests fail.
Remaining work includes:
- Support for client-created request contexts.
- Embedding the browser in a Views hierarchy (cefclient support).
- TryCloseBrowser and DoClose support.
- Most of the CefSettings configuration.
- DevTools protocol and window control (ShowDevTools, ExecuteDevToolsMethod).
- CEF-specific WebUI pages (about, license, webui-hosts).
- Context menu customization (CefContextMenuHandler).
- Auto resize (SetAutoResizeEnabled).
- Zoom settings (SetZoomLevel).
- File dialog runner (RunFileDialog).
- File and JS dialog handlers (CefDialogHandler, CefJSDialogHandler).
- Extension loading (LoadExtension, etc).
- Plugin loading (OnBeforePluginLoad).
- Widevine loading (CefRegisterWidevineCdm).
- PDF and print preview does not display.
- Crash reporting is untested.
- Mac: Web content loads but does not display.
The following ceftests are now passing when run with the
"--enable-chrome-runtime" command-line flag:
CorsTest.*
DisplayTest.*:-DisplayTest.AutoResize
DOMTest.*
DraggableRegionsTest.*
ImageTest.*
MessageRouterTest.*
NavigationTest.*
ParserTest.*
RequestContextTest.*Global*
RequestTest.*
ResourceManagerTest.*
ResourceRequestHandlerTest.*
ResponseTest.*
SchemeHandlerTest.*
ServerTest.*
StreamResourceHandlerTest.*
StreamTest.*
StringTest.*
TaskTest.*
TestServerTest.*
ThreadTest.*
URLRequestTest.*Global*
V8Test.*:-V8Test.OnUncaughtExceptionDevTools
ValuesTest.*
WaitableEventTest.*
XmlReaderTest.*
ZipReaderTest.*
A CORS preflight request is an "OPTIONS" request sent to a server prior to a
cross-origin XMLHttpRequest or Fetch request. The server's response determines
which HTTP request methods are allowed and supported, and whether credentials
such as Cookies and HTTP Authentication should be sent with requests.
A CORS preflight request will only be sent if certain conditions are met. For
example, it will be sent for requests that have potentially unsafe HTTP
methods [1] or request headers [2]. See the NeedsPreflight function in
services/network/cors/cors_url_loader.cc for full details.
CORS preflight functionality is implemented in the network service and will not
be triggered if the client handles the request instead of allowing it to proceed
over the network. Since the preflight request itself also runs in the network
service it cannot be intercepted by the client.
[1] https://fetch.spec.whatwg.org/#cors-safelisted-method
[2] https://fetch.spec.whatwg.org/#cors-safelisted-request-header
The request.trusted_params.isolation_info.site_for_cookies value must
match request.site_for_cookies.
This change also adds unit test coverage for cross-origin GET redirects.
This fixes an IsCanonical() DCHECK failure triggered by calling
CanonicalCookie::Create for a non-cookieable URL.
This change also adds unit test coverage for cross-origin cookie
behavior with sub-resource requests (iframe, XHR, Fetch).
- CefURLRequest::Create is no longer supported in the renderer process
(see https://crbug.com/891872). Use CefFrame::CreateURLRequest instead.
- Mac platform definitions have been changed from `MACOSX` to `MAC`
(see https://crbug.com/1105907) and related CMake macro names have
been updated. The old `OS_MACOSX` define is still set in code and CMake
for backwards compatibility.
- Linux ARM build is currently broken (see https://crbug.com/1123214).
To reduce text execution time and flakyness this change also
introduces a global test server that is initialized when needed
and torn down after all tests have completed.
With site-per-process enabled a spare renderer process will be created
for use with a future browser or navigation. Consequently the
|extra_info| parameter populated in OnRenderProcessThreadCreated will no
longer be delivered to OnRenderThreadCreated in the expected renderer
process. To avoid confusion these callbacks have been removed completely.
After this change CefRenderProcessHandler::OnWebKitInitialized should
be used for startup tasks in the render process, and OnBrowserCreated
should be used in the render process to recieve |extra_info| passed from
CefBrowserHost::CreateBrowser or CefLifeSpanHandler::OnBeforePopup.
- Windows: 10.0.19041 SDK is now required.
- macOS: 10.15.1 SDK (at least Xcode 11.2) is now required.
- Remove CefMediaSource::IsValid and CefMediaSink::IsValid which would
always return true.
This change moves shared resource initialization to a common location and
disables crash reporting initialization in chrome/ code via patch files.
When using the Chrome runtime on macOS the Chrome application window will
display, but web content is currently blank and the application does not
exit cleanly. This will need to be debugged further in the future.
This change adds basic Chrome runtime implementations for CefBrowserContext
and CefBrowserPlatformDelegate. A Chrome browser window with default frame
and styling can now be created using CefBrowserHost::CreateBrowser and some
CefClient callbacks will be triggered via the WebContentsObserver
implementation in CefBrowserHostImpl.
Any additional browser windows created via the Chrome UI will be unmanaged
by CEF. The application message loop will block until all browser windows
have been closed by the user.
Running `cefsimple --enable-chrome-runtime` will create and run a
Chrome browser window using the CEF app methods, and call
CefApp::OnContextInitialized as expected. CEF task methods also
work as expected in the main process. No browser-related methods or
callbacks are currently supported for the Chrome window, and the
application will exit when the last Chrome window closes.
The Chrome runtime requires resources.pak, chrome_100_percent.pak
and chrome_200_percent.pak files which were not previously built
with CEF. It shares the existing locales pak files which have been
updated to include additional Chrome-specific strings.
On Linux, the Chrome runtime requires GTK so use_gtk=true must be
specified via GN_DEFINES when building.
This change also refactors the CEF runtime, which can be tested in
the various supported modes by running:
$ cefclient
$ cefclient --multi-threaded-message-loop
$ cefclient --external-message-pump
This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.
This change includes additional supporting changes:
- Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
callback (see issue #1454).
- Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
- Add a `--devtools-protocol-log-file=<path>` command-line flag for
logging protocol messages sent to/from the DevTools front-end
while it is displayed. This is useful for understanding existing
DevTools protocol usage.
- Add a new "libcef_static_unittests" executable target to support
light-weight unit tests of libcef_static internals (e.g. without
requiring exposure via the CEF API). Files to be unittested are
placed in the new "libcef_static_unittested" source_set which is
then included by both the existing libcef_static library and the
new unittests executable target.
- Linux: Remove use_bundled_fontconfig=false, which is no longer
required and causes unittest build errors (see issue #2424).
This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the `--offline`
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.