Navigation transitions: Block first response until after transitions have run.

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index da9e8239d688412d1bc617f5e35d01c2e6b55b77..f39e56a37c96517a77339d946d6b03dfa430a5dd 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -246,6 +246,10 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   virtual void DidStartLoading(RenderViewHost* render_view_host) {}
   virtual void DidStopLoading(RenderViewHost* render_view_host) {}
 
+  // This method is invoked when the request is deferred immediately after
+  // receiving response headers.
+  virtual void DidDeferAfterResponseStarted() {}

[jam, 2014/06/10 05:54:56]

similarly, since this notification is only consumed inside content, no need to
add this to the public WebContentsObserver. have the code which calls this
callback instead call the one impl of this directly

[shatch, 2014/06/10 20:20:24]

I thought this was needed this to make its way to the java
WebContentsObserverAndroid so that the transition helper can listen for the
event. This gets sent through
RenderFrameHostImpl->WebContentsImpl->WebContentsObserverAndroid->java. Is there
another way to do that?

[jam, 2014/06/11 02:00:21]

WebContentsImpl can call the ContentViewCoreImpl method directly (getting it
through ContentViewCoreImpl::FromWebContents).

[shatch, 2014/06/14 00:41:37]

Ah great, thanks! Moved this to call ContentViewCoreImpl directly and
reimplemented the java side as a listener on ContentViewCore instead.

+
   // When WebContents::Stop() is called, the WebContents stops loading and then
   // invokes this method. If there are ongoing navigations, their respective
   // failure methods will also be invoked.