[cc/metrics] Terminate reporters when begin-frames not expected.

If the client stops requesting begin-frames, then it is unlikely to
submit any compositor-frames for any begin-frame it may still be
handling. So terminate the associated reporters in this case.

BUG=790761

Change-Id: I2db257af67ea1827b97703280c12ab202b9be89e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2146785Reviewed-by: Behdad Bakhshinategh <behdadb@chromium.org>
Commit-Queue: Behdad Bakhshinategh <behdadb@chromium.org>
Auto-Submit: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758909}

cc/metrics/compositor_frame_reporting_controller.cc

@@ -296,6 +296,19 @@ void CompositorFrameReportingController::DidPresentCompositorFrame(
   }
 }
 
+void CompositorFrameReportingController::OnStoppedRequestingBeginFrames() {
+  // If the client stopped requesting begin-frames, that means the begin-frames
+  // currently being handled are no longer expected to produce any
+  // compositor-frames. So terminate the reporters.
+  auto now = Now();
+  for (int i = 0; i < PipelineStage::kNumPipelineStages; ++i) {
+    if (reporters_[i]) {
+      reporters_[i]->TerminateFrame(FrameTerminationStatus::kDidNotProduceFrame,
+                                    now);
+    }
+  }
+}
+
 void CompositorFrameReportingController::SetBlinkBreakdown(
     std::unique_ptr<BeginMainFrameMetrics> details,
     base::TimeTicks main_thread_start_time) {

cc/metrics/compositor_frame_reporting_controller.h

@@ -65,6 +65,7 @@ class CC_EXPORT CompositorFrameReportingController {
   virtual void DidPresentCompositorFrame(
       uint32_t frame_token,
       const viz::FrameTimingDetails& details);
+  void OnStoppedRequestingBeginFrames();
 
   void SetBlinkBreakdown(std::unique_ptr<BeginMainFrameMetrics> details,
                          base::TimeTicks main_thread_start_time);

cc/metrics/compositor_timing_history.cc

@@ -662,6 +662,7 @@ void CompositorTimingHistory::WillFinishImplFrame(bool needs_redraw,
 void CompositorTimingHistory::BeginImplFrameNotExpectedSoon() {
   SetBeginMainFrameNeededContinuously(false);
   SetCompositorDrawingContinuously(false);
+  compositor_frame_reporting_controller_->OnStoppedRequestingBeginFrames();
 }
 
 void CompositorTimingHistory::WillBeginMainFrame(