Require a process ID when looking up RFHs by FrameTreeNode ID.

extensions/browser/extension_navigation_throttle.cc

Index: extensions/browser/extension_navigation_throttle.cc
diff --git a/extensions/browser/extension_navigation_throttle.cc b/extensions/browser/extension_navigation_throttle.cc
index cf4e5e43ca2ccd6a7d94db9b70b4ece2e00dd78c..5d026c5d7d649db24e2476ee38bb38b7353f9b26 100644
--- a/extensions/browser/extension_navigation_throttle.cc
+++ b/extensions/browser/extension_navigation_throttle.cc
@@ -108,18 +108,7 @@ ExtensionNavigationThrottle::WillStartRequest() {
   // The subframe which is navigated needs to have all of its ancestors be
   // at the same origin, otherwise the resource needs to be explicitly listed
   // in web_accessible_resources.
-  // Since the RenderFrameHost is not known until navigation has committed,
-  // we can't get it from NavigationHandle. However, this code only cares about
-  // the ancestor chain, so find the current RenderFrameHost and use it to
-  // traverse up to the main frame.
-  content::RenderFrameHost* navigating_frame =
-      web_contents->FindFrameByFrameTreeNodeId(
-          navigation_handle()->GetFrameTreeNodeId());
-  DCHECK(navigating_frame);
-
-  // Traverse the chain of parent frames, checking if they are the same origin
-  // as the URL of this navigation.
-  content::RenderFrameHost* ancestor = navigating_frame->GetParent();
+  content::RenderFrameHost* ancestor = navigation_handle()->GetParentFrame();

[Charlie Reis, 2017/05/04 16:29:58]

ekaramad/lazyboy: I'm further simplifying your recent refactor from
https://codereview.chromium.org/2858143002, now that we can just grab the parent
RFH directly.  (Otherwise, the FindFrameByFrameTreeNodeId call is a bit risky in
general, in case people tried to use navigating_frame in other ways.)

[EhsanK, 2017/05/04 18:01:38]

Thanks! This is quite useful in my current works so looking forward to a quick
rebase asap. Also I guess it should be more efficient given that we do not check
all frames for a matching ID.

   bool external_ancestor = false;
   while (ancestor) {
     if (ancestor->GetLastCommittedURL().GetOrigin() != url.GetOrigin()) {