Teach navigation throttles how to cancel requests in WillProcessResponse.

content/browser/frame_host/navigation_handle_impl.h

Index: content/browser/frame_host/navigation_handle_impl.h
diff --git a/content/browser/frame_host/navigation_handle_impl.h b/content/browser/frame_host/navigation_handle_impl.h
index 192cdab3348d3d9dc0bd3ff51c92aa625f7e1ae7..c43098cc2ff1ea3f0ab621df351b9b4cdafbc5f9 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -160,6 +160,14 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
       scoped_refptr<net::HttpResponseHeaders> response_headers,
       const ThrottleChecksFinishedCallback& callback);
 
+  // Called when the URLRequest has delivered response headers and metadata.
+  // |callback| will be callwed when all throttle checks have completed,

[clamy, 2016/01/25 16:36:21]

nit: s/callwed/called

[Mike West, 2016/01/26 09:41:41]

Thanks! :)

+  // allowing the caller to cancel the navigation or let it proceed. |callback|
+  // MUST NOT be called with a result of DEFER.

[clamy, 2016/01/25 16:36:21]

s/MUST NOT/will not -> NavigationHandle makes a guarantee that it won't call
|callback| with a result of DEFER.

[Mike West, 2016/01/26 09:41:41]

Done.

+  void WillProcessResponse(
+      scoped_refptr<net::HttpResponseHeaders> response_headers,
+      const ThrottleChecksFinishedCallback& callback);
+
   // Returns the FrameTreeNode this navigation is happening in.
   FrameTreeNode* frame_tree_node() { return frame_tree_node_; }
 
@@ -190,6 +198,7 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
     WILL_REDIRECT_REQUEST,
     DEFERRING_REDIRECT,
     CANCELING,
+    WILL_PROCESS_RESPONSE,

[clamy, 2016/01/25 16:36:21]

Can you add a DEFFERRING_PROCESS_RESPONSE state as well, to match the other
checks?

[Mike West, 2016/01/26 09:41:41]

Done.

     READY_TO_COMMIT,
     DID_COMMIT,
     DID_COMMIT_ERROR_PAGE,
@@ -201,6 +210,7 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
 
   NavigationThrottle::ThrottleCheckResult CheckWillStartRequest();
   NavigationThrottle::ThrottleCheckResult CheckWillRedirectRequest();
+  NavigationThrottle::ThrottleCheckResult CheckWillProcessResponse();
 
   // Helper function to run and reset the |complete_callback_|. This marks the
   // end of a round of NavigationThrottleChecks.