Discardable property support on TabManager

chrome/browser/memory/tab_manager_observer.cc

 // Copyright (c) 2016 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/memory/tab_manager_observer.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace memory {
 
 void TabManagerObserver::OnDiscardedStateChange(content::WebContents* contents,
                                                 bool is_discarded) {}
 
+void TabManagerObserver::OnAutoDiscardableStateChange(
+    content::WebContents* contents,
+    bool is_auto_discardable) {}
+
 TabManagerObserver::~TabManagerObserver() {}
 
 }  // namespace memory