[blink] Support (semi-)transparent background colors in WebView/Frame.

content/renderer/render_view_impl.cc

 // 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/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <memory>
 
@@ skipping 2230 matching lines @@
 
   RenderWidget::OnResize(params);
 
   if (old_visible_viewport_size != visible_viewport_size_)
     has_scrolled_focused_editable_node_into_rect_ = false;
 }
 
 void RenderViewImpl::OnSetBackgroundOpaque(bool opaque) {
   if (frame_widget_)
     frame_widget_->setIsTransparent(!opaque);
-  if (compositor_)
-    compositor_->setHasTransparentBackground(!opaque);
 }
 
 void RenderViewImpl::OnSetActive(bool active) {
   if (webview())
     webview()->setIsActive(active);
 }
 
 blink::WebWidget* RenderViewImpl::GetWebWidget() const {
   if (frame_widget_)
     return frame_widget_;
@@ skipping 457 matching lines @@
                             INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   }
 
   std::unique_ptr<InputEventAck> ack(
       new InputEventAck(InputEventAckSource::MAIN_THREAD, input_event->type(),
                         INPUT_EVENT_ACK_STATE_NOT_CONSUMED));
   OnInputEventAck(std::move(ack));
 }
 
 }  // namespace content