Fix incorrect rendering of background color in out-of-process iframes.

content/renderer/child_frame_compositing_helper.cc

 // Copyright 2014 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/child_frame_compositing_helper.h"
 
 #include <utility>
 
 #include "cc/blink/web_layer_impl.h"
 #include "cc/layers/picture_image_layer.h"
@@ skipping 187 matching lines @@
   scoped_refptr<cc::SurfaceLayer> surface_layer =
       cc::SurfaceLayer::Create(satisfy_callback, require_callback);
   // TODO(oshima): This is a stopgap fix so that the compositor does not
   // scaledown the content when 2x frame data is added to 1x parent frame data.
   // Fix this in cc/.
   if (IsUseZoomForDSFEnabled())
     scale_factor = 1.0f;
 
   surface_layer->SetSurfaceId(surface_id, scale_factor, frame_size);
   surface_layer->SetMasksToBounds(true);
-  blink::WebLayer* layer = new cc_blink::WebLayerImpl(surface_layer);
+  cc_blink::WebLayerImpl* layer = new cc_blink::WebLayerImpl(surface_layer);
+  // TODO(lfg): Investigate if it's possible to propagate the information about
+  // the child surface's opacity. https://crbug.com/629851.
+  layer->setOpaque(false);
+  layer->SetContentsOpaqueIsFixed(true);
   UpdateWebLayer(layer);
 
   UpdateVisibility(true);
 
   // The RWHV creates a destruction dependency on the surface that needs to be
   // satisfied. Note: render_frame_proxy_ is null in the case our client is a
   // BrowserPlugin; in this case the BrowserPlugin sends its own SatisfySequence
   // message.
   if (render_frame_proxy_) {
     render_frame_proxy_->Send(
         new FrameHostMsg_SatisfySequence(host_routing_id_, sequence));
   } else if (browser_plugin_.get()) {
     browser_plugin_->SendSatisfySequence(sequence);
   }
 
   CheckSizeAndAdjustLayerProperties(
       frame_size, scale_factor,
       static_cast<cc_blink::WebLayerImpl*>(web_layer_.get())->layer());
 }
 
 void ChildFrameCompositingHelper::UpdateVisibility(bool visible) {
   if (web_layer_)
     web_layer_->setDrawsContent(visible);
 }
 
 }  // namespace content