Clarify that WebContents::GetLastCommittedURL returns the virtual URL.

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 96b14ef6da138ec6f3241f3cab915ac7f10822ed..24a500ff82b6d3859511ed8ea76a99b5f228291f 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -38,6 +38,10 @@ class CONTENT_EXPORT NavigationHandle {
 
   // 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.