Remove redundant WebContents field in WebContentsObserver implementation

chrome/browser/dom_distiller/tab_utils.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/dom_distiller/tab_utils.h"
 
 #include "base/message_loop/message_loop.h"
 #include "chrome/browser/dom_distiller/dom_distiller_service_factory.h"
 #include "chrome/browser/ui/tab_contents/core_tab_helper.h"
 #include "chrome/browser/ui/tab_contents/core_tab_helper_delegate.h"
@@ skipping 43 matching lines @@
   virtual void WebContentsDestroyed() OVERRIDE;
 
   // Takes ownership of the ViewerHandle to keep distillation alive until |this|
   // is deleted.
   void TakeViewerHandle(scoped_ptr<ViewerHandle> viewer_handle);
 
  private:
   // The handle to the view request towards the DomDistillerService. It
   // needs to be kept around to ensure the distillation request finishes.
   scoped_ptr<ViewerHandle> viewer_handle_;
-
-  // The WebContents this class is tracking.
-  content::WebContents* web_contents_;
 };
 
 void SelfDeletingRequestDelegate::DidNavigateMainFrame(
     const content::LoadCommittedDetails& details,
     const content::FrameNavigateParams& params) {
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 void SelfDeletingRequestDelegate::RenderProcessGone(
     base::TerminationStatus status) {
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 void SelfDeletingRequestDelegate::WebContentsDestroyed() {
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 SelfDeletingRequestDelegate::SelfDeletingRequestDelegate(
     content::WebContents* web_contents)
-    : web_contents_(web_contents) {
-  content::WebContentsObserver::Observe(web_contents_);
+    : WebContentsObserver(web_contents) {
 }
 
 SelfDeletingRequestDelegate::~SelfDeletingRequestDelegate() {
-  content::WebContentsObserver::Observe(NULL);
 }
 
 void SelfDeletingRequestDelegate::OnArticleReady(
     const DistilledArticleProto* article_proto) {
 }
 
 void SelfDeletingRequestDelegate::OnArticleUpdated(
     ArticleDistillationUpdate article_update) {
 }
 
@@ skipping 49 matching lines @@
   new_web_contents->GetController().CopyStateFrom(
       old_web_contents->GetController());
 
   CoreTabHelper::FromWebContents(old_web_contents)->delegate()->SwapTabContents(
       old_web_contents, new_web_contents, false, false);
 
   StartNavigationToDistillerViewer(new_web_contents,
                                    old_web_contents->GetLastCommittedURL());
   StartDistillation(old_web_contents);
 }