Remove RenderWidget::SetBackground, change IPC to pass a bool.

content/browser/renderer_host/render_widget_host_view_base.cc

Index: content/browser/renderer_host/render_widget_host_view_base.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_base.cc b/content/browser/renderer_host/render_widget_host_view_base.cc
index c7eafc246fa074b54c5c5af21279cbd884004018..c6e3c613e1ba86c718d00db55c38d278aed8482c 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.cc
+++ b/content/browser/renderer_host/render_widget_host_view_base.cc
@@ -367,6 +367,7 @@ const int kFlushInputRateInUs = 16666;
 
 RenderWidgetHostViewBase::RenderWidgetHostViewBase()
     : popup_type_(blink::WebPopupTypeNone),
+      background_opaque_(true),
       mouse_locked_(false),
       showing_context_menu_(false),
       selection_text_offset_(0),
@@ -385,12 +386,12 @@ bool RenderWidgetHostViewBase::OnMessageReceived(const IPC::Message& msg){
   return false;
 }
 
-void RenderWidgetHostViewBase::SetBackground(const SkBitmap& background) {
-  background_ = background;
+void RenderWidgetHostViewBase::SetBackgroundOpaque(bool opaque) {
+  background_opaque_ = opaque;
 }
 
-const SkBitmap& RenderWidgetHostViewBase::GetBackground() {
-  return background_;
+bool RenderWidgetHostViewBase::GetBackgroundOpaque() {
+  return background_opaque_;
 }
 
 gfx::Size RenderWidgetHostViewBase::GetPhysicalBackingSize() const {