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

4 files changed, 37 insertions, 33 deletions

diff --git a/base/system_monitor.cc b/base/system_monitor.cc
index cf946a7..44cdce5 100644
--- a/base/system_monitor.cc
+++ b/base/system_monitor.cc
@@ -60,17 +60,17 @@ void SystemMonitor::RemoveObserver(PowerObserver* obs) {
 void SystemMonitor::NotifyPowerStateChange() {
   LOG(INFO) << L"PowerStateChange: "
            << (BatteryPower() ? L"On" : L"Off") << L" battery";
-  observer_list_->Notify(&PowerObserver::OnPowerStateChange, this);
+  observer_list_->Notify(&PowerObserver::OnPowerStateChange, BatteryPower());
 }
 
 void SystemMonitor::NotifySuspend() {
   LOG(INFO) << L"Power Suspending";
-  observer_list_->Notify(&PowerObserver::OnSuspend, this);
+  observer_list_->Notify(&PowerObserver::OnSuspend);
 }
 
 void SystemMonitor::NotifyResume() {
   LOG(INFO) << L"Power Resuming";
-  observer_list_->Notify(&PowerObserver::OnResume, this);
+  observer_list_->Notify(&PowerObserver::OnResume);
 }
 
 // static
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.
diff --git a/base/system_monitor_unittest.cc b/base/system_monitor_unittest.cc
index 0ca8d61..ff39d87 100644
--- a/base/system_monitor_unittest.cc
+++ b/base/system_monitor_unittest.cc
@@ -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.
 
@@ -14,9 +14,17 @@ class PowerTest : public base::SystemMonitor::PowerObserver {
       resumes_(0) {};
 
   // PowerObserver callbacks.
-  void OnPowerStateChange(base::SystemMonitor*) { power_state_changes_++; };
-  void OnSuspend(base::SystemMonitor*) { suspends_++; };
-  void OnResume(base::SystemMonitor*) { resumes_++; };
+  void OnPowerStateChange(bool on_battery_power) {
+    power_state_changes_++;
+  }
+
+  void OnSuspend() {
+    suspends_++;
+  }
+
+  void OnResume() {
+    resumes_++;
+  }
 
   // Test status counts.
   bool battery() { return battery_; }
@@ -39,40 +47,40 @@ TEST(SystemMonitor, PowerNotifications) {
   // Initialize time() since it registers as a SystemMonitor observer.
   base::Time now = base::Time::Now();
 
-  base::SystemMonitor* monitor = base::SystemMonitor::Get();
+  base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
   PowerTest test[kObservers];
   for (int index = 0; index < kObservers; ++index)
-    monitor->AddObserver(&test[index]);
+    system_monitor->AddObserver(&test[index]);
 
   // Send a bunch of power changes.  Since the battery power hasn't
   // actually changed, we shouldn't get notifications.
   for (int index = 0; index < 5; index++) {
-    monitor->ProcessPowerMessage(base::SystemMonitor::POWER_STATE_EVENT);
+    system_monitor->ProcessPowerMessage(base::SystemMonitor::POWER_STATE_EVENT);
     EXPECT_EQ(test[0].power_state_changes(), 0);
   }
 
   // Sending resume when not suspended should have no effect.
-  monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
+  system_monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
   loop.RunAllPending();
   EXPECT_EQ(test[0].resumes(), 0);
 
   // Pretend we suspended.
-  monitor->ProcessPowerMessage(base::SystemMonitor::SUSPEND_EVENT);
+  system_monitor->ProcessPowerMessage(base::SystemMonitor::SUSPEND_EVENT);
   loop.RunAllPending();
   EXPECT_EQ(test[0].suspends(), 1);
 
   // Send a second suspend notification.  This should be suppressed.
-  monitor->ProcessPowerMessage(base::SystemMonitor::SUSPEND_EVENT);
+  system_monitor->ProcessPowerMessage(base::SystemMonitor::SUSPEND_EVENT);
   loop.RunAllPending();
   EXPECT_EQ(test[0].suspends(), 1);
 
   // Pretend we were awakened.
-  monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
+  system_monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
   loop.RunAllPending();
   EXPECT_EQ(test[0].resumes(), 1);
 
   // Send a duplicate resume notification.  This should be suppressed.
-  monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
+  system_monitor->ProcessPowerMessage(base::SystemMonitor::RESUME_EVENT);
   loop.RunAllPending();
   EXPECT_EQ(test[0].resumes(), 1);
 }
diff --git a/base/time_win.cc b/base/time_win.cc
index c134a9e..9fdcab1 100644
--- a/base/time_win.cc
+++ b/base/time_win.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 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.
 
@@ -104,29 +104,25 @@ class HighResolutionTimerManager : public base::SystemMonitor::PowerObserver {
     if (is_monitoring_)
       return;
     is_monitoring_ = true;
-    base::SystemMonitor* system = base::SystemMonitor::Get();
-    DCHECK(system);
-    system->AddObserver(this);
-    UseHiResClock(!system->BatteryPower());
+    base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
+    system_monitor->AddObserver(this);
+    UseHiResClock(!system_monitor->BatteryPower());
   }
 
   void StopMonitoring() {
     if (!is_monitoring_)
       return;
     is_monitoring_ = false;
-    base::SystemMonitor* monitor = base::SystemMonitor::Get();
-    if (monitor)
-      monitor->RemoveObserver(this);
+    base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
+    if (system_monitor)
+      system_monitor->RemoveObserver(this);
   }
 
   // Interfaces for monitoring Power changes.
-  void OnPowerStateChange(base::SystemMonitor* system) {
-    UseHiResClock(!system->BatteryPower());
+  void OnPowerStateChange(bool on_battery_power) {
+    UseHiResClock(!on_battery_power);
   }
 
-  void OnSuspend(base::SystemMonitor* system) {}
-  void OnResume(base::SystemMonitor* system) {}
-
  private:
   HighResolutionTimerManager()
       : is_monitoring_(false),