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..13c647d63de2c33a17055f5bafdfd478e2438e23 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -82,9 +82,10 @@ class CONTENT_EXPORT NavigationHandle {
   // 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;
 
   // The WebContents the navigation is taking place in.
   WebContents* GetWebContents();