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

content/public/browser/navigation_handle.h

Index: content/public/browser/navigation_handle.h
diff --git a/content/public/browser/navigation_handle.h b/content/public/browser/navigation_handle.h
index 684fd26aa145b62a67505afb0e6db0e3a5ab4456..67550b048550342300f9701af0d4d3cc484ba2ea 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -86,6 +86,11 @@ class CONTENT_EXPORT NavigationHandle {
   // taking place in the main frame, the value returned is -1.

[ncarter (slow), 2017/05/01 22:15:32]

Deprecate this?

[Charlie Reis, 2017/05/01 22:36:51]

Interesting.  Yes, the only other caller is
ExtensionApiFrameIdMap::GetParentFrameId, and that could just call
GetFrameTreeNodeId on GetParentFrame.

Done.

   virtual int GetParentFrameTreeNodeId() = 0;
 
+  // Returns the RenderFrameHost for the parent frame, or nullptr if this
+  // navigation is taking place in the main frame. This value will not change
+  // during a navigation.
+  virtual RenderFrameHost* GetParentFrame() = 0;
+
   // The WebContents the navigation is taking place in.
   WebContents* GetWebContents();