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

content/public/browser/navigation_handle.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 #define CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 64 matching lines @@
   //  * redirect via the <meta http-equiv="refresh"> tag
   //  * using window.history.pushState
   virtual bool IsRendererInitiated() = 0;
 
   // Returns the FrameTreeNode ID for the frame in which the navigation is
   // performed. This ID is browser-global and uniquely identifies a frame that
   // hosts content. The identifier is fixed at the creation of the frame and
   // stays constant for the lifetime of the frame.
   virtual int GetFrameTreeNodeId() = 0;
 
-  // Returns the FrameTreeNode ID for the parent frame. If this navigation is
-  // taking place in the main frame, the value returned is -1.
-  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;

[Devlin, 2017/05/02 02:04:29]

If we were worried before about callers storing the render frame tree node id
and not expected a change, is this better?  Is it safer to store a raw ptr to a
RenderFrameHost?

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

Yes, since the parent RenderFrameHost doesn't change during the navigation, and
the navigation would be canceled if it did.  (More specifically, a cross-process
navigation in the parent FrameTreeNode will synchronously delete the subtree of
FrameTreeNodes and RenderFrameHosts, which will delete any of their
NavigationHandles as well.  Same if the parent is detached or closed.)
I don't think this should be a problem, given that we already expose a raw
pointer to this frame's RenderFrameHost below (after the NavigationHandle is
ready to commit).  Exposing the FTN ID here just seemed to be a hurdle to the
actual uses, which wasn't adding much value in the NavigationHandle case when
there's no risk of it changing.

 
   // The WebContents the navigation is taking place in.
   WebContents* GetWebContents();
 
   // The time the navigation started, recorded either in the renderer or in the
   // browser process. Corresponds to Navigation Timing API.
   virtual const base::TimeTicks& NavigationStart() = 0;
 
   // Whether or not the navigation was started within a context menu.
   virtual bool WasStartedFromContextMenu() const = 0;
@@ skipping 197 matching lines @@
 
   // The NavigationData that the embedder returned from
   // ResourceDispatcherHostDelegate::GetNavigationData during commit. This will
   // be a clone of the NavigationData.
   virtual NavigationData* GetNavigationData() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_