Reduce precision on RAF timestamp

Bug: 838328
Change-Id: I3b0ba96d4351bdd48467e58a2a58d6dbfe11b163
Reviewed-on: https://chromium-review.googlesource.com/1052167Reviewed-by: Justin Novosad <junov@chromium.org>
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557212}

third_party/blink/renderer/core/workers/worker_animation_frame_provider.cc

@@ -28,7 +28,10 @@ void WorkerAnimationFrameProvider::CancelCallback(int id) {
 }
 
 void WorkerAnimationFrameProvider::BeginFrame() {
-  double time = WTF::TimeTicksInSeconds(WTF::CurrentTimeTicks()) * 1000;
+  double time = WTF::CurrentTimeTicksInMilliseconds();
+  // We don't want to expose microseconds residues to users.
+  time = round(time * 60) / 60;
+
   callback_collection_.ExecuteCallbacks(time, time);
 
   for (auto& ctx : rendering_contexts_) {