cc: Fix and simplify DelayBasedTimeSource

- This converts some floating point math to integer math
to avoid rounding errors.

- Assigns last_tick_time_ to be the time it was *supposed*
to tick and no longer uses it as a synonym for "now".

- Adds trace events to help debug when the interval or
phase changes.

BUG=256650

Review URL: https://chromiumcodereview.appspot.com/18589002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210101 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 1 insertions, 8 deletions

diff --git a/cc/scheduler/delay_based_time_source.h b/cc/scheduler/delay_based_time_source.h
index 1dc4d6f..009b9a3 100644
--- a/cc/scheduler/delay_based_time_source.h
+++ b/cc/scheduler/delay_based_time_source.h
@@ -47,12 +47,6 @@ class CC_EXPORT DelayBasedTimeSource : public TimeSource {
   void PostNextTickTask(base::TimeTicks now);
   void OnTimerFired();
 
-  enum State {
-    STATE_INACTIVE,
-    STATE_STARTING,
-    STATE_ACTIVE,
-  };
-
   struct Parameters {
     Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
         : interval(interval), tick_target(tick_target) {}
@@ -61,7 +55,6 @@ class CC_EXPORT DelayBasedTimeSource : public TimeSource {
   };
 
   TimeSourceClient* client_;
-  bool has_tick_target_;
   base::TimeTicks last_tick_time_;
 
   // current_parameters_ should only be written by PostNextTickTask.
@@ -71,7 +64,7 @@ class CC_EXPORT DelayBasedTimeSource : public TimeSource {
   Parameters current_parameters_;
   Parameters next_parameters_;
 
-  State state_;
+  bool active_;
 
   base::SingleThreadTaskRunner* task_runner_;
   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;