Transfer theme & page background colors between changes of RWHV.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 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/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 3892 matching lines @@
                     RenderViewHostChanged(old_host, new_host));
 
   // Ensure that the associated embedder gets cleared after a RenderViewHost
   // gets swapped, so we don't reuse the same embedder next time a
   // RenderViewHost is attached to this WebContents.
   RemoveBrowserPluginEmbedder();
 }
 
 void WebContentsImpl::NotifyFrameSwapped(RenderFrameHost* old_host,
                                          RenderFrameHost* new_host) {
+  // Pass the background color of the old host to the new one. This passes
+  // on the page background color of the old host (or the theme color if the
+  // page background color is not set). This avoids flashes of white when
+  // starting up new_host.
+  if (old_host && old_host->GetView() && new_host && new_host->GetView()) {
+    new_host->GetView()->SetBackgroundColor(
+        old_host->GetView()->background_color());

[no sievers, 2016/05/17 18:05:43]

You said this doesn't work reliably. Does it work better if you set the color
from RenderFrameHostManager::Navigate() where we call
delegate_->CreateRenderViewForRenderManager()?

The other way to make this a bit more robust would be to make the
background_color a property of the WebContentsView and then
WebContentsView::CreateViewForWidget() could set the right background color
immediately.

+  }
+
   FOR_EACH_OBSERVER(WebContentsObserver,
                     observers_,
                     RenderFrameHostChanged(old_host, new_host));
 }
 
 // TODO(avi): Remove this entire function because this notification is already
 // covered by two observer functions. http://crbug.com/170921
 void WebContentsImpl::NotifyDisconnected() {
   if (!notify_disconnection_)
     return;
@@ skipping 1092 matching lines @@
   for (RenderViewHost* render_view_host : render_view_host_set)
     render_view_host->OnWebkitPreferencesChanged();
 }
 
 void WebContentsImpl::SetJavaScriptDialogManagerForTesting(
     JavaScriptDialogManager* dialog_manager) {
   dialog_manager_ = dialog_manager;
 }
 
 }  // namespace content