FrameMetrics: Adding frame metrics analysis to LayerTreeHostImpl

Added frame metrics analysis to LayerTreeHostImpl. The frame presentation
callback times are sent to frame metrics for every nth scrolling.

Bug:851088

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I32aee9b5401c056ed3be64e17a45cc1958188199
Reviewed-on: https://chromium-review.googlesource.com/1147921
Commit-Queue: Yi Xu <yiyix@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581782}

cc/trees/layer_tree_host_impl.cc

@@ -119,6 +119,11 @@ namespace {
 // V1 saw errors of ~0.065 between computed window and content widths.
 const float kMobileViewportWidthEpsilon = 0.15f;
 
+// We report frames and their display time to the FrameMetrics to analyze fps
+// for every |kFrameMetricsScrollReportFrequency|th scroll event after the last
+// report.
+const int kFrameMetricsScrollReportFrequency = 10;
+
 bool HasFixedPageScale(LayerTreeImpl* active_tree) {
   return active_tree->min_page_scale_factor() ==
          active_tree->max_page_scale_factor();
@@ -1908,13 +1913,17 @@ viz::CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() {
 
   active_tree_->GetViewportSelection(&metadata.selection);
 
+  // Skip recording frame metrics for android_webview
+  // (using_synchronous_renderer_compositor) scrolls because different
+  // application is handling frame presentation in android webview.
   if (active_tree_->has_presentation_callbacks() ||
-      settings_.always_request_presentation_time) {
+      settings_.always_request_presentation_time ||
+      (scroll_events_after_reporting_ == 0 && CurrentlyScrollingNode() &&
+       !settings_.using_synchronous_renderer_compositor)) {
     metadata.request_presentation_feedback = true;
     frame_token_infos_.emplace_back(metadata.frame_token,
                                     CurrentBeginFrameArgs().frame_time,
                                     active_tree_->TakePresentationCallbacks());
-
     DCHECK_LE(frame_token_infos_.size(), 25u);
   }
 
@@ -4410,6 +4419,14 @@ void LayerTreeHostImpl::ScrollEndImpl(ScrollState* scroll_state) {
   DistributeScrollDelta(scroll_state);
   browser_controls_offset_manager_->ScrollEnd();
   ClearCurrentlyScrollingNode();
+
+  // At the end of a scrolling event, increases |scroll_events_after_reporting_|
+  // by 1. If it is the |kFrameMetricsScrollReportFrequency| scrolling event
+  // after the previous report to the frame metrics, then
+  // |scroll_events_after_reporting_| becomes 0 and the data will be reported
+  // back the frame metrics.
+  scroll_events_after_reporting_ =
+      (scroll_events_after_reporting_ + 1) % kFrameMetricsScrollReportFrequency;
 }
 
 void LayerTreeHostImpl::ScrollEnd(ScrollState* scroll_state, bool should_snap) {

cc/trees/layer_tree_host_impl.h

@@ -1102,6 +1102,9 @@ class CC_EXPORT LayerTreeHostImpl
   ui::FrameMetrics frame_metrics_;
   ui::SkippedFrameTracker skipped_frame_tracker_;
   bool is_animating_for_snap_;
+  // The number of scroll events happened after the last report to frame
+  // metrics.
+  int scroll_events_after_reporting_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };