Send initializeChildFrame from RenderFrameProxy rather than WebLocalFrame (part 2).

Move initializeChildFrame from RenderFrameImpl to RenderFrameProxy.  Replace RenderFrameImpl::OnSwapOut's call to setIsRemote with WebRemoteFrame::initializeFromFrame that was introduced in part 1 of this change (https://codereview.chromium.org/591413004/)

This will be followed by another CL that will remove setIsRemote on the blink side.

BUG=416102

Review URL: https://codereview.chromium.org/592263002

Cr-Commit-Position: refs/heads/master@{#296822}
diff --git a/content/renderer/render_frame_proxy.h b/content/renderer/render_frame_proxy.h
index 495e439..a73a8f2 100644
--- a/content/renderer/render_frame_proxy.h
+++ b/content/renderer/render_frame_proxy.h
@@ -99,6 +99,9 @@
       blink::WebRemoteFrame* targetFrame,
       blink::WebSecurityOrigin target,
       blink::WebDOMMessageEvent event);
+  virtual void initializeChildFrame(
+      const blink::WebRect& frame_rect,
+      float scale_factor);
 
  private:
   RenderFrameProxy(int routing_id, int frame_routing_id);