Remove AboutToNavigateRenderFrame, issue custom notification for DevTools.

content/browser/frame_host/navigator_delegate.h

Index: content/browser/frame_host/navigator_delegate.h
diff --git a/content/browser/frame_host/navigator_delegate.h b/content/browser/frame_host/navigator_delegate.h
index 1494cc339f2ed24e5dcbc75f86475349a36489c1..79fb7966936040bd680bc2d6d4a3789f0fa135e5 100644
--- a/content/browser/frame_host/navigator_delegate.h
+++ b/content/browser/frame_host/navigator_delegate.h
@@ -97,11 +97,6 @@ class CONTENT_EXPORT NavigatorDelegate {
   // WebContents::NotifyNavigationStateChanged.
   virtual void NotifyChangedNavigationState(InvalidateTypes changed_flags) {}
 
-  // Notifies the Navigator embedder that it is beginning to navigate a frame.
-  virtual void AboutToNavigateRenderFrame(
-      RenderFrameHostImpl* old_host,
-      RenderFrameHostImpl* new_host) {}
-
   // Notifies the Navigator embedder that a navigation to the pending
   // NavigationEntry has started in the browser process.
   virtual void DidStartNavigationToPendingEntry(