Move most of the remaining users of WebContentsObserver::tab_contents() to use web_contents().

content/browser/tab_contents/tab_contents.cc

 // Copyright (c) 2011 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 "content/browser/tab_contents/tab_contents.h"
 
 #include <cmath>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 1572 matching lines @@
 
 content::RendererPreferences TabContents::GetRendererPrefs(
     content::BrowserContext* browser_context) const {
   return renderer_preferences_;
 }
 
 TabContents* TabContents::GetAsTabContents() {
   return this;
 }
 
+WebContents* TabContents::GetAsWebContents() {
+  return this;
+}
+
 content::ViewType TabContents::GetRenderViewType() const {
   return view_type_;
 }
 
 void TabContents::RenderViewCreated(RenderViewHost* render_view_host) {
   content::NotificationService::current()->Notify(
       content::NOTIFICATION_RENDER_VIEW_HOST_CREATED_FOR_TAB,
       content::Source<TabContents>(this),
       content::Details<RenderViewHost>(render_view_host));
   NavigationEntry* entry = controller_.GetActiveEntry();
@@ skipping 606 matching lines @@
   encoding_ = content::GetContentClient()->browser()->
       GetCanonicalEncodingNameByAliasName(encoding);
 }
 
 void TabContents::CreateViewAndSetSizeForRVH(RenderViewHost* rvh) {
   RenderWidgetHostView* rwh_view = GetView()->CreateViewForWidget(rvh);
   // Can be NULL during tests.
   if (rwh_view)
     rwh_view->SetSize(GetView()->GetContainerSize());
 }