Give the main frame a RenderWidget.

content/browser/frame_host/render_frame_host_impl.cc

 // Copyright 2013 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/frame_host/render_frame_host_impl.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
@@ skipping 914 matching lines @@
 void RenderFrameHostImpl::OnDidDropNavigation() {
   // At the end of Navigate(), the FrameTreeNode's DidStartLoading is called to
   // force the spinner to start, even if the renderer didn't yet begin the load.
   // If it turns out that the renderer dropped the navigation, the spinner needs
   // to be turned off.
   frame_tree_node_->DidStopLoading();
   navigation_handle_.reset();
 }
 
 RenderWidgetHostImpl* RenderFrameHostImpl::GetRenderWidgetHost() {
-  if (render_widget_host_)
-    return render_widget_host_;
-
   // TODO(kenrb): When RenderViewHost no longer inherits RenderWidgetHost,
   // we can remove this fallback. Currently it is only used for the main
   // frame.
   if (!GetParent())
     return static_cast<RenderWidgetHostImpl*>(render_view_host_);
 
+  if (render_widget_host_)
+    return render_widget_host_;
+
   return nullptr;
 }
 
 RenderWidgetHostView* RenderFrameHostImpl::GetView() {
-  RenderFrameHostImpl* frame = this;
-  while (frame) {
+  // TODO(dcheng): Similar to above, though the main RenderFrameHost now has a

[ncarter (slow), 2015/09/03 20:24:37]

It's not clear what "similar to above" refers to in this context. Could you make
the comment stand-alone?

[dcheng, 2015/09/03 21:29:24]

Done.

+  // RenderWidgetHost, a lot of the plumbing is still missing. Thus, for now,
+  // the main frame always uses the RVH's view. https://crbug.com/526958
+  for (RenderFrameHostImpl* frame = this; frame->GetParent();
+       frame = static_cast<RenderFrameHostImpl*>(frame->GetParent())) {
     if (frame->render_widget_host_)
       return frame->render_widget_host_->GetView();
-    frame = static_cast<RenderFrameHostImpl*>(frame->GetParent());
   }
 
   return render_view_host_->GetView();
 }
 
 int RenderFrameHostImpl::GetEnabledBindings() {
   return render_view_host_->GetEnabledBindings();
 }
 
 void RenderFrameHostImpl::SetNavigationHandle(
@@ skipping 1262 matching lines @@
             BrowserPluginInstanceIDToAXTreeID(value)));
         break;
       case AX_CONTENT_INT_ATTRIBUTE_LAST:
         NOTREACHED();
         break;
     }
   }
 }
 
 }  // namespace content