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

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 <objc/runtime.h>
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/basictypes.h"
@@ skipping 2037 matching lines @@
     if (!EnsureCompositedIOSurface())
       GotAcceleratedCompositingError();
   }
 }
 
 void RenderWidgetHostViewMac::ShowDefinitionForSelection() {
   RenderWidgetHostViewMacDictionaryHelper helper(this);
   helper.ShowDefinitionForSelection();
 }
 
-void RenderWidgetHostViewMac::SetBackground(const SkBitmap& background) {
-  RenderWidgetHostViewBase::SetBackground(background);
+void RenderWidgetHostViewMac::SetBackgroundOpaque(bool opaque) {
+  RenderWidgetHostViewBase::SetBackgroundOpaque(opaque);
   if (render_widget_host_)
-    render_widget_host_->Send(new ViewMsg_SetBackground(
-        render_widget_host_->GetRoutingID(), background));
+    render_widget_host_->SetBackgroundOpaque(opaque);
 }
 
 void RenderWidgetHostViewMac::CreateBrowserAccessibilityManagerIfNeeded() {
   if (!GetBrowserAccessibilityManager()) {
     SetBrowserAccessibilityManager(
         new BrowserAccessibilityManagerMac(
             cocoa_view_,
             BrowserAccessibilityManagerMac::GetEmptyDocument(),
             render_widget_host_));
   }
@@ skipping 2234 matching lines @@
 }
 
 - (void)disableRendering {
   // Disable the fade-out animation as the layer is removed.
   ScopedCAActionDisabler disabler;
   [self removeFromSuperlayer];
   renderWidgetHostView_ = nil;
 }
 
 @end  // implementation SoftwareLayer