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]`

tests/cefclient/browser/root_window_manager.cc

@@ -10,7 +10,7 @@
 #include "include/base/cef_logging.h"
 #include "include/wrapper/cef_closure_task.h"
 #include "include/wrapper/cef_helpers.h"
-#include "tests/cefclient/browser/client_handler_std.h"
+#include "tests/cefclient/browser/default_client_handler.h"
 #include "tests/cefclient/browser/main_context.h"
 #include "tests/cefclient/browser/test_runner.h"
 #include "tests/shared/browser/extension_util.h"
@@ -39,7 +39,7 @@ class ClientRequestContextHandler : public CefRequestContextHandler,
     CefRefPtr<CefCommandLine> command_line =
         CefCommandLine::GetGlobalCommandLine();
 
-    if (!main_context->UseChromeRuntime() &&
+    if (!main_context->UseChromeBootstrap() &&
         command_line->HasSwitch(switches::kLoadExtension)) {
       // Alloy implementation for loading extensions. Chrome runtime handles
       // this internally.
@@ -113,6 +113,40 @@ class ClientRequestContextHandler : public CefRequestContextHandler,
   DISALLOW_COPY_AND_ASSIGN(ClientRequestContextHandler);
 };
 
+// Ensure a compatible set of window creation attributes.
+void SanityCheckWindowConfig(const bool is_devtools,
+                             bool& use_views,
+                             bool& use_alloy_style,
+                             bool& with_osr) {
+  if (MainContext::Get()->UseChromeBootstrap()) {
+    if (is_devtools && use_alloy_style) {
+      LOG(WARNING)
+          << "Alloy style is not supported with Chrome runtime DevTools;"
+             " using Chrome style.";
+      use_alloy_style = false;
+    }
+
+    if (is_devtools && !use_views) {
+      LOG(WARNING)
+          << "Native parent is not supported with Chrome runtime DevTools;"
+             " using Views.";
+      use_views = true;
+    }
+  }
+
+  if (!use_alloy_style && with_osr) {
+    LOG(WARNING) << "Windowless rendering is not supported with Chrome style;"
+                    " using windowed rendering.";
+    with_osr = false;
+  }
+
+  if (use_views && with_osr) {
+    LOG(WARNING) << "Windowless rendering is not supported with Views;"
+                    " using windowed rendering.";
+    with_osr = false;
+  }
+}
+
 }  // namespace
 
 RootWindowManager::RootWindowManager(bool terminate_when_all_windows_closed)
@@ -136,8 +170,11 @@ scoped_refptr<RootWindow> RootWindowManager::CreateRootWindow(
   CefBrowserSettings settings;
   MainContext::Get()->PopulateBrowserSettings(&settings);
 
+  SanityCheckWindowConfig(/*is_devtools=*/false, config->use_views,
+                          config->use_alloy_style, config->with_osr);
+
   scoped_refptr<RootWindow> root_window = RootWindow::Create(
-      MainContext::Get()->UseViews(), /*parent_window=*/nullptr);
+      config->use_views, config->use_alloy_style);
   root_window->Init(this, std::move(config), settings);
 
   // Store a reference to the root window on the main thread.
@@ -147,22 +184,23 @@ scoped_refptr<RootWindow> RootWindowManager::CreateRootWindow(
 }
 
 scoped_refptr<RootWindow> RootWindowManager::CreateRootWindowAsPopup(
-    scoped_refptr<RootWindow> parent_window,
+    bool use_views,
+    bool use_alloy_style,
     bool with_controls,
     bool with_osr,
+    bool is_devtools,
     const CefPopupFeatures& popupFeatures,
     CefWindowInfo& windowInfo,
     CefRefPtr<CefClient>& client,
     CefBrowserSettings& settings) {
   CEF_REQUIRE_UI_THREAD();
 
-  MainContext::Get()->PopulateBrowserSettings(&settings);
+  SanityCheckWindowConfig(is_devtools, use_views, use_alloy_style, with_osr);
 
   if (MainContext::Get()->UseDefaultPopup()) {
     // Use default window creation for the popup. A new |client| instance is
     // still required by cefclient architecture.
-    client = new ClientHandlerStd(/*delegate=*/nullptr, with_controls,
-                                  /*startup_url=*/CefString());
+    client = new DefaultClientHandler();
     return nullptr;
   }
 
@@ -171,11 +209,10 @@ scoped_refptr<RootWindow> RootWindowManager::CreateRootWindowAsPopup(
     temp_window_.reset(new TempWindow());
   }
 
-  const bool use_views = parent_window ? parent_window->IsViewsHosted()
-                                       : MainContext::Get()->UseViews();
+  MainContext::Get()->PopulateBrowserSettings(&settings);
 
   scoped_refptr<RootWindow> root_window =
-      RootWindow::Create(use_views, parent_window);
+      RootWindow::Create(use_views, use_alloy_style);
   root_window->InitAsPopup(this, with_controls, with_osr, popupFeatures,
                            windowInfo, client, settings);
 
@@ -363,7 +400,7 @@ CefRefPtr<CefRequestContext> RootWindowManager::CreateRequestContext(
   if (request_context_per_browser_) {
     // Synchronous use of non-global request contexts is not safe with the
     // Chrome runtime.
-    CHECK(!callback.is_null() || !MainContext::Get()->UseChromeRuntime());
+    CHECK(!callback.is_null() || !MainContext::Get()->UseChromeBootstrap());
 
     // Create a new request context for each browser.
     CefRequestContextSettings settings;