Surface synchronization: Don't report blocked duration of throttled children

A child can be "throttled" for an arbitrary length of time if it is never
embedded. This skews blocked duration metrics. Simply don't report those
metrics if a surface is blocked on a parent.

Bug: 890767
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel
Change-Id: I3c8a8494a5b1e5a973b2e5c2b61cffe5c2b76f6f
Reviewed-on: https://chromium-review.googlesource.com/c/1274591
Commit-Queue: Fady Samuel <fsamuel@chromium.org>
Reviewed-by: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598886}

components/viz/service/surfaces/surface.cc

@@ -198,6 +198,11 @@ void Surface::OnSurfaceDependencyAdded() {
 
   DCHECK(frame_sink_id_dependencies_.empty());
 
+  // Cancel the deadline and don't report UMA. The UMA metrics are only
+  // meaningful for activation dependencies and not throttling.
+  deadline_->CancelWithoutReport();
+  DCHECK(!deadline_->has_deadline());
+
   // All blockers have been cleared. The surface can be activated now.
   ActivatePendingFrame(base::nullopt);
 }

components/viz/service/surfaces/surface_dependency_deadline.cc

@@ -41,6 +41,13 @@ base::Optional<base::TimeDelta> SurfaceDependencyDeadline::Cancel() {
   return CancelInternal(false);
 }
 
+void SurfaceDependencyDeadline::CancelWithoutReport() {
+  if (!deadline_)
+    return;
+  begin_frame_source_->RemoveObserver(this);
+  deadline_.reset();
+}
+
 void SurfaceDependencyDeadline::InheritFrom(
     const SurfaceDependencyDeadline& other) {
   if (*this == other)
@@ -96,8 +103,7 @@ base::Optional<base::TimeDelta> SurfaceDependencyDeadline::CancelInternal(
   if (!deadline_)
     return base::nullopt;
 
-  begin_frame_source_->RemoveObserver(this);
-  deadline_.reset();
+  CancelWithoutReport();
 
   base::TimeDelta duration = tick_clock_->NowTicks() - start_time_;
 

components/viz/service/surfaces/surface_dependency_deadline.h

@@ -36,6 +36,12 @@ class VIZ_SERVICE_EXPORT SurfaceDependencyDeadline : public BeginFrameObserver {
   // deadline set, then return base::nullopt.
   base::Optional<base::TimeDelta> Cancel();
 
+  // If a deadline had been set, then cancel the deadline and don't
+  // generate a UMA report. When a surface activation has been throttled
+  // then the time to activation could be arbitrarily delayed and may
+  // skew metrics.
+  void CancelWithoutReport();
+
   bool has_deadline() const { return deadline_.has_value(); }
 
   base::Optional<base::TimeTicks> deadline_for_testing() const {