Reland #1: Fix re-usage of stale cached WebPreferences in RenderViewHost.

content/shell/browser/layout_test/blink_test_controller.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/shell/browser/layout_test/blink_test_controller.h"
 
 #include <stddef.h>
 
 #include <iostream>
 #include <set>
@@ skipping 274 matching lines @@
   if (test_url.spec().find("W3C-SVG-1.1") != std::string::npos)
     initial_size_ = gfx::Size(kTestSVGWindowWidthDip, kTestSVGWindowHeightDip);
   if (!main_window_) {
     main_window_ = content::Shell::CreateNewWindow(
         browser_context,
         GURL(),
         NULL,
         initial_size_);
     WebContentsObserver::Observe(main_window_->web_contents());
     current_pid_ = base::kNullProcessId;
+    default_prefs_ =
+      main_window_->web_contents()->GetRenderViewHost()->GetWebkitPreferences();
     main_window_->LoadURL(test_url);
   } else {
 #if defined(OS_MACOSX)
     // Shell::SizeTo is not implemented on all platforms.
     main_window_->SizeTo(initial_size_);
 #endif
     main_window_->web_contents()
         ->GetRenderViewHost()
         ->GetWidget()
         ->GetView()
         ->SetSize(initial_size_);
     main_window_->web_contents()
         ->GetRenderViewHost()
         ->GetWidget()
         ->WasResized();
     RenderViewHost* render_view_host =
         main_window_->web_contents()->GetRenderViewHost();
-    WebPreferences prefs = render_view_host->GetWebkitPreferences();
-    OverrideWebkitPrefs(&prefs);

[Mike West, 2016/07/08 13:16:37]

I think you still need to call this against `default_prefs_`.

[carlosk, 2016/07/11 08:21:00]

The default we save up there @ 295 does already include those so we don't have
to do that here again.

When the new RenderView is created with a call to
RenderViewHostImpl::CreateRenderView, it initializes its preferences  by calling
GetWebkitPreferences() which ends up calling
BlinkTestController::OverrideWebkitPrefs through the test specific
implementation of LayoutTestContentBrowserClient::OverrideWebkitPrefs.

-    render_view_host->UpdateWebkitPreferences(prefs);
+    render_view_host->UpdateWebkitPreferences(default_prefs_);
     HandleNewRenderFrameHost(render_view_host->GetMainFrame());
 
     NavigationController::LoadURLParams params(test_url);
     params.transition_type = ui::PageTransitionFromInt(
         ui::PAGE_TRANSITION_TYPED | ui::PAGE_TRANSITION_FROM_ADDRESS_BAR);
     params.should_clear_history_list = true;
     main_window_->web_contents()->GetController().LoadURLWithParams(params);
     main_window_->web_contents()->Focus();
   }
   main_window_->web_contents()->GetRenderViewHost()->GetWidget()->SetActive(
@@ skipping 425 matching lines @@
       render_view_host->GetRoutingID(), stitched_layout_dump));
 }
 
 void BlinkTestController::OnPrintMessage(const std::string& message) {
   printer_->AddMessageRaw(message);
 }
 
 void BlinkTestController::OnOverridePreferences(const WebPreferences& prefs) {
   should_override_prefs_ = true;
   prefs_ = prefs;
+
+  // Notifies the main RenderViewHost that Blink preferences changed so
+  // immediately apply the new settings and to avoid re-usage of cached
+  // preferences that are now stale. RenderViewHost::UpdateWebkitPreferences is
+  // not used here because it would send an unneeded preferences update to the
+  // renderer.
+  RenderViewHost* main_render_view_host =
+      main_window_->web_contents()->GetRenderViewHost();
+  main_render_view_host->OnWebkitPreferencesChanged();
 }
 
 void BlinkTestController::OnClearDevToolsLocalStorage() {
   ShellBrowserContext* browser_context =
       ShellContentBrowserClient::Get()->browser_context();
   StoragePartition* storage_partition =
       BrowserContext::GetStoragePartition(browser_context, NULL);
   storage_partition->GetDOMStorageContext()->DeleteLocalStorage(
       content::LayoutTestDevToolsFrontend::GetDevToolsPathAsURL("", "")
           .GetOrigin());
@@ skipping 158 matching lines @@
   } else {
     printer_->AddErrorMessage(base::StringPrintf(
         "FAIL: Unexpected sendBluetoothManualChooserEvent() event name '%s'.",
         event_name.c_str()));
     return;
   }
   bluetooth_chooser_factory_->SendEvent(event, argument);
 }
 
 }  // namespace content