[content] Fix background color update handling in RWHVAura.

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index 47e3577c6c788d3bd3e38dcf576522e6298a310b..79ff74f003d712a4e093c13d59843b3508dcc14c 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -57,6 +57,7 @@ RenderWidgetHostViewChildFrame::RenderWidgetHostViewChildFrame(
       last_compositor_frame_sink_id_(0),
       current_surface_scale_factor_(1.f),
       frame_connector_(nullptr),
+      background_color_(SK_ColorWHITE),
       weak_factory_(this) {
   id_allocator_.reset(new cc::LocalSurfaceIdAllocator());
   GetSurfaceManager()->RegisterFrameSinkId(frame_sink_id_);
@@ -213,9 +214,15 @@ RenderWidgetHostViewChildFrame::GetNativeViewAccessible() {
 }
 
 void RenderWidgetHostViewChildFrame::SetBackgroundColor(SkColor color) {
-  RenderWidgetHostViewBase::SetBackgroundColor(color);
-  bool opaque = GetBackgroundOpaque();
-  host_->SetBackgroundOpaque(opaque);
+  background_color_ = color;
+
+  DCHECK(SkColorGetA(color) == SK_AlphaOPAQUE ||
+         SkColorGetA(color) == SK_AlphaTRANSPARENT);
+  host_->SetBackgroundOpaque(SkColorGetA(color) == SK_AlphaOPAQUE);
+}
+
+SkColor RenderWidgetHostViewChildFrame::background_color() const {
+  return background_color_;
 }
 
 gfx::Size RenderWidgetHostViewChildFrame::GetPhysicalBackingSize() const {