Clarify that WebContents::GetLastCommittedURL returns the virtual URL.

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 "content/common/content_export.h"
@@ skipping 20 matching lines @@
  public:
   virtual ~NavigationHandle() {}
 
   // Parameters available at navigation start time -----------------------------
   //
   // These parameters are always available during the navigation. Note that
   // some may change during navigation (e.g. due to server redirects).
 
   // The URL the frame is navigating to. This may change during the navigation
   // when encountering a server redirect.
+  // This URL may not be the same as the virtual URL returned from
+  // WebContents::GetVisibleURL and WebContents::GetLastCommittedURL. For
+  // example, viewing a page's source navigates to the URL of the page, but the
+  // virtual URL is prefixed with "view-source:".
   virtual const GURL& GetURL() = 0;
 
   // Whether the navigation is taking place in the main frame or in a subframe.
   // This remains constant over the navigation lifetime.
   virtual bool IsInMainFrame() = 0;
 
   // Whether the navigation is taking place in a frame that is a direct child
   // of the main frame. This remains constant over the navigation lifetime.
   virtual bool IsParentMainFrame() = 0;
 
@@ skipping 134 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_