Transfer theme & page background colors between changes of RWHV.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 51d18a0b1a43a10a6ce486dac2d2a40ee032d1b5..ad40aebbd9e63fdcce4c91bfdf52898ad47e5ed5 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -1061,6 +1061,16 @@ void RenderWidgetHostViewAura::OnSwapCompositorFrame(
     std::unique_ptr<cc::CompositorFrame> frame) {
   TRACE_EVENT0("content", "RenderWidgetHostViewAura::OnSwapCompositorFrame");
 
+  // Override the background color to the current compositor background.
+  // This allows us to, when navigating to a new page, transfer this color
+  // (via code in ContentsWebView) between the current RenderWidgetHost and
+  // the new one, avoiding a flash of the theme color in between.
+  // See crbug.com/470669.
+  // Setting the page's background color here should also have better quality
+  // output in cases when the window's root layer peeks out from the content
+  // layers.
+  SetBackgroundColor(frame->metadata.root_background_color);
+
   last_scroll_offset_ = frame->metadata.root_scroll_offset;
   if (!frame->delegated_frame_data)
     return;