Make WebContentsImpl aware of all of its RWHs.

content/browser/renderer_host/render_widget_host_delegate.h

Index: content/browser/renderer_host/render_widget_host_delegate.h
diff --git a/content/browser/renderer_host/render_widget_host_delegate.h b/content/browser/renderer_host/render_widget_host_delegate.h
index 61c2feb8e1832e1027d9422e98f6a38d69ff4312..b4e4169529bb7e11b1e8da0b392852b01cfdcac1 100644
--- a/content/browser/renderer_host/render_widget_host_delegate.h
+++ b/content/browser/renderer_host/render_widget_host_delegate.h
@@ -39,6 +39,9 @@ struct NativeWebKeyboardEvent;
 //  of the RenderWidgetHost.
 class CONTENT_EXPORT RenderWidgetHostDelegate {
  public:
+  // The RenderWidgetHost has just been created.
+  virtual void RenderWidgetCreated(RenderWidgetHostImpl* render_widget_host) {}
+
   // The RenderWidgetHost is going to be deleted.
   virtual void RenderWidgetDeleted(RenderWidgetHostImpl* render_widget_host) {}