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/3848002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@63176 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: 8f31f41edbe94651e1df889993be0704954942db
diff --git a/base/message_loop.cc b/base/message_loop.cc
index 8f6c997..0b03d3c 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -179,6 +179,16 @@
 
   // 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 @@
       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 @@
   // 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 @@
   // 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.