Enhance chrome.app.window API with window background color

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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/renderer_host/render_widget_host_view_mac.h"
 
 #import <Carbon/Carbon.h>
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
@@ skipping 1632 matching lines @@
 void RenderWidgetHostViewMac::SetBackgroundColor(SkColor color) {
   if (color == background_color_)
     return;
 
   RenderWidgetHostViewBase::SetBackgroundColor(color);
   bool opaque = GetBackgroundOpaque();
 
   if (render_widget_host_)
     render_widget_host_->SetBackgroundOpaque(opaque);
 
+  if (opaque && color != SK_ColorWHITE)
+    render_widget_host_->SetBaseBackgroundColor(color);
+
   [cocoa_view_ setOpaque:opaque];
 
   browser_compositor_->SetHasTransparentBackground(!opaque);
 
   ScopedCAActionDisabler disabler;
   base::ScopedCFTypeRef<CGColorRef> cg_color(
       skia::CGColorCreateFromSkColor(color));
   [background_layer_ setBackgroundColor:cg_color];
 }
 
@@ skipping 1826 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end