Revert 70142 - Fix build error

chrome/test/automation/tab_proxy.h

 // Copyright (c) 2010 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 CHROME_TEST_AUTOMATION_TAB_PROXY_H_
 #define CHROME_TEST_AUTOMATION_TAB_PROXY_H_
 #pragma once
 
 #include "build/build_config.h"  // NOLINT
 
@@ skipping 30 matching lines @@
   MEDIUM_FONT = 16,
   LARGE_FONT = 24,
   LARGEST_FONT = 36
 };
 
 class TabProxy : public AutomationResourceProxy,
                  public JavaScriptExecutionController {
  public:
   class TabProxyDelegate {
    public:
-    virtual bool OnMessageReceived(TabProxy* tab, const IPC::Message& msg) {
-      return false;
-    }
+    virtual bool OnMessageReceived(TabProxy* tab, const IPC::Message& msg) {}
     virtual void OnChannelError(TabProxy* tab) {}
 
    protected:
     virtual ~TabProxyDelegate() {}
   };
 
   TabProxy(AutomationMessageSender* sender,
            AutomationHandleTracker* tracker,
            int handle);
 
@@ skipping 361 matching lines @@
   // purposes.
   void LastObjectRemoved();
 
  private:
   Lock list_lock_;  // Protects the observers_list_.
   ObserverList<TabProxyDelegate> observers_list_;
   DISALLOW_COPY_AND_ASSIGN(TabProxy);
 };
 
 #endif  // CHROME_TEST_AUTOMATION_TAB_PROXY_H_