Change chrome from statically enabling high resolution timers on windows

to enabling them dynamically - only when the application really needs
them.

I am working on some test cases for this, and will add them.  But wanted
to send out the concept for review.

In this implementation, I modify the message loop to detect when the
application has requested high resolution timers.  Note that there are
multiple MessageLoops active in a single process.  After a period of
time, we simply shut it off again.    We could have set a timer or
kept a count of active timers, or any number of more complex algorithms.
But I think this algorithm is very simple and good enough.  If an
application continues needing high resolution timers for more than 1s,
we'll turn the high-resolution timers back on again.

One last change - since we've implemented the clamp at 4ms, there isn't
a lot of point to our use of 1ms for timeBeginPeriod.  I've modified
that to 2 (which is half of 4ms, our target minimal interval).

BUG=46531
TEST=MessageLoop.HighResolutionTimers


Review URL: http://codereview.chromium.org/2822035

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@51102 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 1 insertions, 3 deletions

diff --git a/app/hi_res_timer_manager_win.cc b/app/hi_res_timer_manager_win.cc
index b7cee1d..6fbffca 100644
--- a/app/hi_res_timer_manager_win.cc
+++ b/app/hi_res_timer_manager_win.cc
@@ -25,7 +25,5 @@ void HighResolutionTimerManager::OnPowerStateChange(bool on_battery_power) {
 void HighResolutionTimerManager::UseHiResClock(bool use) {
   if (use == hi_res_clock_used_)
     return;
-  bool result = base::Time::UseHighResolutionTimer(use);
-  DCHECK(result);
-  hi_res_clock_used_ = use;
+  base::Time::EnableHighResolutionTimer(use);
 }