Simplify the PowerObserver API by removing unneeded args and providing default implementations.

This also makes all the subclasses use the same code to add/remove observers.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/244054

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27740 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 5 deletions

diff --git a/base/system_monitor.h b/base/system_monitor.h
index aeec42b..71d8436 100644
--- a/base/system_monitor.h
+++ b/base/system_monitor.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2009 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.
 
@@ -44,7 +44,7 @@ class SystemMonitor {
 
   // Is the computer currently on battery power.
   // Can be called on any thread.
-  bool BatteryPower() {
+  bool BatteryPower() const {
     // Using a lock here is not necessary for just a bool.
     return battery_in_use_;
   }
@@ -65,13 +65,13 @@ class SystemMonitor {
    public:
     // Notification of a change in power status of the computer, such
     // as from switching between battery and A/C power.
-    virtual void OnPowerStateChange(SystemMonitor*) = 0;
+    virtual void OnPowerStateChange(bool on_battery_power) {}
 
     // Notification that the system is suspending.
-    virtual void OnSuspend(SystemMonitor*) = 0;
+    virtual void OnSuspend() {}
 
     // Notification that the system is resuming.
-    virtual void OnResume(SystemMonitor*) = 0;
+    virtual void OnResume() {}
   };
 
   // Add a new observer.