chrome: Add support for Alloy style browsers and windows (see #3681)

Split the Alloy runtime into bootstrap and style components. Support
creation of Alloy style browsers and windows with the Chrome runtime.
Chrome runtime (`--enable-chrome-runtime`) + Alloy style
(`--use-alloy-style`) supports Views (`--use-views`), native parent
(`--use-native`) and windowless rendering
(`--off-screen-rendering-enabled`).

Print preview is supported in all cases except with windowless rendering
on all platforms and native parent on MacOS. It is disabled by default
with Alloy style for legacy compatibility. Where supported it can be
enabled or disabled globally using `--[enable|disable]-print-preview` or
configured on a per-RequestContext basis using the
`printing.print_preview_disabled` preference. It also behaves as
expected when triggered via the PDF viewer print button.

Chrome runtime + Alloy style behavior differs from Alloy runtime in the
following significant ways:

- Supports Chrome error pages by default.
- DevTools popups are Chrome style only (cannot be windowless).
- The Alloy extension API will not supported.

Chrome runtime + Alloy style passes all expected Alloy ceftests except
the following:

- `DisplayTest.AutoResize` (Alloy extension API not supported)
- `DownloadTest.*` (Download API not yet supported)
- `ExtensionTest.*` (Alloy extension API not supported)

This change also adds Chrome runtime support for
CefContextMenuHandler::RunContextMenu (see #3293).

This change also explicitly blocks (and doesn't retry) FrameAttached
requests from PDF viewer and print preview excluded frames (see #3664).

Known issues specific to Chrome runtime + Alloy style:
- DevTools popup with windowless rendering doesn't load successfully.
  Use windowed rendering or remote debugging as a workaround.
- Chrome style Window with Alloy style BrowserView (`--use-alloy-style
  --use-chrome-style-window`) does not show Chrome theme changes.

To test:
- Run `ceftests --enable-chrome-runtime --use-alloy-style
       [--use-chrome-style-window] [--use-views|--use-native]
       --gtest_filter=...`
- Run `cefclient --enable-chrome-runtime --use-alloy-style
       [--use-chrome-style-window]
       [--use-views|--use-native|--off-screen-rendering-enabled]`
- Run `cefsimple --enable-chrome-runtime --use-alloy-style [--use-views]`

libcef/browser/extensions/browser_extensions_util.h

@@ -13,45 +13,22 @@
 
 namespace content {
 class BrowserContext;
-struct GlobalRenderFrameHostId;
-class RenderFrameHost;
-class RenderViewHost;
 class WebContents;
 }  // namespace content
 
-class CefBrowserHostBase;
 class AlloyBrowserHostImpl;
 
 namespace extensions {
 
 class Extension;
 
-// Populates |guests| with all guest WebContents with the specified |owner|.
-void GetAllGuestsForOwnerContents(content::WebContents* owner,
-                                  std::vector<content::WebContents*>* guests);
-
 // Returns the WebContents that owns the specified |guest|, if any.
-content::WebContents* GetOwnerForGuestContents(content::WebContents* guest);
+content::WebContents* GetOwnerForGuestContents(
+    const content::WebContents* guest);
 
-// Returns the CefBrowserHostBase that owns the host identified by the specified
-// global ID, if any. |is_guest_view| will be set to true if the ID
-// matches a guest view associated with the returned browser instead of the
-// browser itself.
-CefRefPtr<CefBrowserHostBase> GetOwnerBrowserForGlobalId(
-    const content::GlobalRenderFrameHostId& global_id,
-    bool* is_guest_view);
-
-// Returns the CefBrowserHostBase that owns the specified |host|, if any.
-// |is_guest_view| will be set to true if the host matches a guest view
-// associated with the returned browser instead of the browser itself.
-// TODO(cef): Delete the RVH variant once the remaining use case
-// (via AlloyContentBrowserClient::OverrideWebkitPrefs) has been removed.
-CefRefPtr<CefBrowserHostBase> GetOwnerBrowserForHost(
-    content::RenderViewHost* host,
-    bool* is_guest_view);
-CefRefPtr<CefBrowserHostBase> GetOwnerBrowserForHost(
-    content::RenderFrameHost* host,
-    bool* is_guest_view);
+// Test for different types of guest contents.
+bool IsBrowserPluginGuest(const content::WebContents* web_contents);
+bool IsPrintPreviewDialog(const content::WebContents* web_contents);
 
 // Returns the browser matching |tab_id| and |browser_context|. Returns false if
 // |tab_id| is < 0 or a matching browser cannot be found within