Magnifier: Prevent useless operation in enabling/disabling magnifier.

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

 // Copyright (c) 2012 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/chromeos/chrome_browser_main_chromeos.h"
 
 #include <string>
 #include <vector>
 
 #include "ash/shell.h"
@@ skipping 509 matching lines @@
   // Initialize the brightness observer so that we'll display an onscreen
   // indication of brightness changes during login.
   brightness_observer_.reset(new BrightnessObserver());
   output_observer_.reset(new OutputObserver());
   resume_observer_.reset(new ResumeObserver());
   screen_lock_observer_.reset(new ScreenLockObserver());
   if (KioskModeSettings::Get()->IsKioskModeEnabled()) {
     power_state_override_ = new PowerStateOverride(
         PowerStateOverride::BLOCK_DISPLAY_SLEEP);
   }
-  magnification_manager_.reset(
-      chromeos::MagnificationManager::CreateInstance());
+  chromeos::MagnificationManager::GetInstance()->Initialize();
   chromeos::accessibility::Initialize();
 
   primary_display_switch_observer_.reset(
       new PrimaryDisplaySwitchObserver());
 
   removable_device_notifications_ =
       new RemovableDeviceNotificationsCros();
 
   // Initialize the network portal detector for Chrome OS. The network
   // portal detector starts to listen for notifications from
@@ skipping 77 matching lines @@
   }
 
   // Tell DeviceSettingsService to stop talking to session_manager.
   DeviceSettingsService::Get()->Shutdown();
 
   // We should remove observers attached to D-Bus clients before
   // DBusThreadManager is shut down.
   screen_lock_observer_.reset();
   resume_observer_.reset();
   brightness_observer_.reset();
   output_observer_.reset();

[stevenjb, 2012/12/04 01:35:34]

Having a MagnificationManager instance live past here could cause a number of
subtle shutdown bugs (e.g. accessing a destroyed Profile or ash::Shell). Much
better for code that might accidentally call MagnificationManager::GetInstance()
after this point to crash immediately on a NULL reference.

[yoshiki, 2012/12/04 08:30:20]

I see, I added back removal of the instance.

On 2012/12/04 01:35:34, stevenjb (chromium) wrote:

-  magnification_manager_.reset();
   power_state_override_ = NULL;
 
   // The XInput2 event listener needs to be shut down earlier than when
   // Singletons are finally destroyed in AtExitManager.
   XInputHierarchyChangedEventListener::GetInstance()->Stop();
 
   // chromeos::SystemKeyEventListener::Shutdown() is always safe to call,
   // even if Initialize() wasn't called.
   SystemKeyEventListener::Shutdown();
   imageburner::BurnManager::Shutdown();
@@ skipping 61 matching lines @@
     } else if (trial->group() == margin_200mb) {
       LOG(WARNING) << "low_mem: Part of '200MB' experiment";
       LowMemoryObserver::SetLowMemoryMargin(200);
     } else {
       LOG(WARNING) << "low_mem: Part of 'default' experiment";
     }
   }
 }
 
 }  //  namespace chromeos