2nd try:

Fix regression where high resolution timers could be activated even under
battery power.  Add unit test to protect chromium from developers like me
in the future.

The fix is a one-liner in hi_res_timer_manager_win.cc.  The rest of the code
change is the mechanics to enable the unit test.

BUG=59528
TEST=HiResTimerManagerTest.ToggleOnOff

Review URL: http://codereview.chromium.org/3889004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@63191 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 103 insertions, 12 deletions

diff --git a/app/app.gyp b/app/app.gyp
index 2c8e7f7..538b73d 100644
--- a/app/app.gyp
+++ b/app/app.gyp
@@ -41,6 +41,7 @@
         'animation_container_unittest.cc',
         'animation_unittest.cc',
         'clipboard/clipboard_unittest.cc',
+        'hi_res_timer_manager_unittest.cc',
         'l10n_util_mac_unittest.mm',
         'l10n_util_unittest.cc',
         'multi_animation_unittest.cc',
diff --git a/app/hi_res_timer_manager.h b/app/hi_res_timer_manager.h
index 7eed795..fdc10b3 100644
--- a/app/hi_res_timer_manager.h
+++ b/app/hi_res_timer_manager.h
@@ -18,11 +18,14 @@ class HighResolutionTimerManager : public SystemMonitor::PowerObserver {
   // SystemMonitor::PowerObserver:
   void OnPowerStateChange(bool on_battery_power);
 
+  // Returns true if the hi resolution clock could be used right now.
+  bool hi_res_clock_available() const { return hi_res_clock_available_; }
+
  private:
   // Enable or disable the faster multimedia timer.
   void UseHiResClock(bool use);
 
-  bool hi_res_clock_used_;
+  bool hi_res_clock_available_;
 
   DISALLOW_COPY_AND_ASSIGN(HighResolutionTimerManager);
 };
diff --git a/app/hi_res_timer_manager_posix.cc b/app/hi_res_timer_manager_posix.cc
index 1398449..8a9a41f 100644
--- a/app/hi_res_timer_manager_posix.cc
+++ b/app/hi_res_timer_manager_posix.cc
@@ -7,7 +7,7 @@
 // On POSIX we don't need to do anything special with the system timer.
 
 HighResolutionTimerManager::HighResolutionTimerManager()
-    : hi_res_clock_used_(false) {
+    : hi_res_clock_available_(false) {
 }
 
 HighResolutionTimerManager::~HighResolutionTimerManager() {
diff --git a/app/hi_res_timer_manager_unittest.cc b/app/hi_res_timer_manager_unittest.cc
new file mode 100644
index 0000000..1e7dbc3
--- /dev/null
+++ b/app/hi_res_timer_manager_unittest.cc
@@ -0,0 +1,51 @@
+// 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.
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+#include "app/hi_res_timer_manager.h"
+#include "app/system_monitor.h"
+#include "base/time.h"
+
+#if defined(OS_WIN)
+TEST(HiResTimerManagerTest, ToggleOnOff) {
+  MessageLoop loop;
+  scoped_ptr<SystemMonitor> system_monitor(new SystemMonitor());
+  HighResolutionTimerManager manager;
+
+  // At this point, we don't know if the high resolution timers are on or off,
+  // it depends on what system the tests are running on (for example, if this
+  // test is running on a laptop/battery, then the SystemMonitor would have
+  // already set the PowerState to battery power; but if we're running on a
+  // desktop, then the PowerState will be non-battery power).  Simulate a power
+  // level change to get to a deterministic state.
+  manager.OnPowerStateChange(/* on_battery */ false);
+
+  // Loop a few times to test power toggling.
+  for (int loop = 2; loop >= 0; --loop) {
+    // The manager has the high resolution clock enabled now.
+    EXPECT_TRUE(manager.hi_res_clock_available());
+    // But the Time class has it off, because it hasn't been activated.
+    EXPECT_FALSE(base::Time::IsHighResolutionTimerInUse());
+
+    // Activate the high resolution timer.
+    base::Time::ActivateHighResolutionTimer(true);
+    EXPECT_TRUE(base::Time::IsHighResolutionTimerInUse());
+
+    // Simulate a on-battery power event.
+    manager.OnPowerStateChange(/* on_battery */ true);
+    EXPECT_FALSE(manager.hi_res_clock_available());
+    EXPECT_FALSE(base::Time::IsHighResolutionTimerInUse());
+
+    // Simulate a off-battery power event.
+    manager.OnPowerStateChange(/* on_battery */ false);
+    EXPECT_TRUE(manager.hi_res_clock_available());
+    EXPECT_TRUE(base::Time::IsHighResolutionTimerInUse());
+
+    // De-activate the high resolution timer.
+    base::Time::ActivateHighResolutionTimer(false);
+  }
+}
+#endif  // defined(OS_WIN)
+
diff --git a/app/hi_res_timer_manager_win.cc b/app/hi_res_timer_manager_win.cc
index 6fbffca..da25d70 100644
--- a/app/hi_res_timer_manager_win.cc
+++ b/app/hi_res_timer_manager_win.cc
@@ -7,7 +7,7 @@
 #include "base/time.h"
 
 HighResolutionTimerManager::HighResolutionTimerManager()
-    : hi_res_clock_used_(false) {
+    : hi_res_clock_available_(false) {
   SystemMonitor* system_monitor = SystemMonitor::Get();
   system_monitor->AddObserver(this);
   UseHiResClock(!system_monitor->BatteryPower());
@@ -23,7 +23,8 @@ void HighResolutionTimerManager::OnPowerStateChange(bool on_battery_power) {
 }
 
 void HighResolutionTimerManager::UseHiResClock(bool use) {
-  if (use == hi_res_clock_used_)
+  if (use == hi_res_clock_available_)
     return;
+  hi_res_clock_available_ = use;
   base::Time::EnableHighResolutionTimer(use);
 }
diff --git a/base/message_loop.cc b/base/message_loop.cc
index 8f6c997b..0b03d3c 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -179,6 +179,16 @@ MessageLoop::~MessageLoop() {
 
   // OK, now make it so that no one can find us.
   lazy_tls_ptr.Pointer()->Set(NULL);
+
+#if defined(OS_WIN)
+  // If we left the high-resolution timer activated, deactivate it now.
+  // Doing this is not-critical, it is mainly to make sure we track
+  // the high resolution timer activations properly in our unit tests.
+  if (!high_resolution_timer_expiration_.is_null()) {
+    Time::ActivateHighResolutionTimer(false);
+    high_resolution_timer_expiration_ = base::TimeTicks();
+  }
+#endif
 }
 
 void MessageLoop::AddDestructionObserver(
@@ -337,9 +347,10 @@ void MessageLoop::PostTask_Helper(
       bool needs_high_res_timers =
           delay_ms < (2 * Time::kMinLowResolutionThresholdMs);
       if (needs_high_res_timers) {
-        Time::ActivateHighResolutionTimer(true);
-        high_resolution_timer_expiration_ = base::TimeTicks::Now() +
-            TimeDelta::FromMilliseconds(kHighResolutionTimerModeLeaseTimeMs);
+        if (Time::ActivateHighResolutionTimer(true)) {
+          high_resolution_timer_expiration_ = base::TimeTicks::Now() +
+              TimeDelta::FromMilliseconds(kHighResolutionTimerModeLeaseTimeMs);
+        }
       }
     }
 #endif
diff --git a/base/time.h b/base/time.h
index 79e30b4..305ca6b 100644
--- a/base/time.h
+++ b/base/time.h
@@ -283,10 +283,16 @@ class Time {
   // Activates or deactivates the high resolution timer based on the |activate|
   // flag.  If the HighResolutionTimer is not Enabled (see
   // EnableHighResolutionTimer), this function will return false.  Otherwise
-  // returns true.
+  // returns true.  Each successful activate call must be paired with a
+  // subsequent deactivate call.
   // All callers to activate the high resolution timer must eventually call
   // this function to deactivate the high resolution timer.
   static bool ActivateHighResolutionTimer(bool activate);
+
+  // Returns true if the high resolution timer is both enabled and activated.
+  // This is provided for testing only, and is not tracked in a thread-safe
+  // way.
+  static bool IsHighResolutionTimerInUse();
 #endif
 
   // Converts an exploded structure representing either the local time or UTC
@@ -405,6 +411,9 @@ class Time {
   // when using battery power, we might elect to prevent high speed timers
   // which would draw more power.
   static bool high_resolution_timer_enabled_;
+  // Count of activations on the high resolution timer.  Only use in tests
+  // which are single threaded.
+  static int high_resolution_timer_activated_;
 #endif
 
   // Time in microseconds in UTC.
diff --git a/base/time_win.cc b/base/time_win.cc
index 5d3ecd6..502dd83 100644
--- a/base/time_win.cc
+++ b/base/time_win.cc
@@ -99,6 +99,7 @@ void InitializeClock() {
 const int64 Time::kTimeTToMicrosecondsOffset = GG_INT64_C(11644473600000000);
 
 bool Time::high_resolution_timer_enabled_ = false;
+int Time::high_resolution_timer_activated_ = 0;
 
 // static
 Time Time::Now() {
@@ -162,22 +163,36 @@ void Time::EnableHighResolutionTimer(bool enable) {
 }
 
 // static
-bool Time::ActivateHighResolutionTimer(bool activate) {
-  if (!high_resolution_timer_enabled_)
+bool Time::ActivateHighResolutionTimer(bool activating) {
+  if (!high_resolution_timer_enabled_ && activating)
     return false;
 
   // Using anything other than 1ms makes timers granular
   // to that interval.
   const int kMinTimerIntervalMs = 1;
   MMRESULT result;
-  if (activate)
+  if (activating) {
     result = timeBeginPeriod(kMinTimerIntervalMs);
-  else
+    high_resolution_timer_activated_++;
+  } else {
     result = timeEndPeriod(kMinTimerIntervalMs);
+    high_resolution_timer_activated_--;
+  }
   return result == TIMERR_NOERROR;
 }
 
 // static
+bool Time::IsHighResolutionTimerInUse() {
+  // Note:  we should track the high_resolution_timer_activated_ value
+  // under a lock if we want it to be accurate in a system with multiple
+  // message loops.  We don't do that - because we don't want to take the
+  // expense of a lock for this.  We *only* track this value so that unit
+  // tests can see if the high resolution timer is on or off.
+  return high_resolution_timer_enabled_ &&
+      high_resolution_timer_activated_ > 0;
+}
+
+// static
 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
   // Create the system struct representing our exploded time. It will either be
   // in local time or UTC.