[cleanup] cc: Remove an unused field.

CompositorTimingHistory::submit_ack_watchdog_enabled_ used to be used
for reporting Scheduling.*.SwapAckWasFast metrics, but these were
removed in crrev.com/575177. So |submit_ack_watchdog_enabled_| field is
removed in this CL.

BUG=none

Change-Id: I9c188e305623b9ec3214f37c603573de5682a6d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1706954Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678542}

cc/scheduler/compositor_timing_history.cc

@@ -77,9 +77,6 @@ const double kPrepareTilesEstimationPercentile = 90.0;
 const double kActivateEstimationPercentile = 90.0;
 const double kDrawEstimationPercentile = 90.0;
 
-constexpr base::TimeDelta kSubmitAckWatchdogTimeout =
-    base::TimeDelta::FromSeconds(8);
-
 // This macro is deprecated since its bucket count uses too much bandwidth.
 // It also has sub-optimal range and bucket distribution.
 // TODO(brianderson): Delete this macro and associated UMAs once there is
@@ -423,7 +420,6 @@ CompositorTimingHistory::CompositorTimingHistory(
       activate_duration_history_(kDurationHistorySize),
       draw_duration_history_(kDurationHistorySize),
       begin_main_frame_on_critical_path_(false),
-      submit_ack_watchdog_enabled_(false),
       uma_reporter_(CreateUMAReporter(uma_category)),
       rendering_stats_instrumentation_(rendering_stats_instrumentation),
       compositor_frame_reporting_controller_(
@@ -559,7 +555,6 @@ void CompositorTimingHistory::DidCreateAndInitializeLayerTreeFrameSink() {
   // After we get a new output surface, we won't get a spurious
   // CompositorFrameAck from the old output surface.
   submit_start_time_ = base::TimeTicks();
-  submit_ack_watchdog_enabled_ = false;
 }
 
 void CompositorTimingHistory::WillBeginImplFrame(
@@ -582,14 +577,6 @@ void CompositorTimingHistory::WillBeginImplFrame(
     SetBeginMainFrameCommittingContinuously(false);
   }
 
-  if (submit_ack_watchdog_enabled_) {
-    base::TimeDelta submit_not_acked_time_ = now - submit_start_time_;
-    if (submit_not_acked_time_ >= kSubmitAckWatchdogTimeout) {
-      // Only record this UMA once per submitted CompositorFrame.
-      submit_ack_watchdog_enabled_ = false;
-    }
-  }
-
   if (frame_type == viz::BeginFrameArgs::NORMAL)
     uma_reporter_->AddBeginImplFrameLatency(now - frame_time);
 
@@ -926,7 +913,6 @@ void CompositorTimingHistory::DidSubmitCompositorFrame(uint32_t frame_token) {
   DCHECK_EQ(base::TimeTicks(), submit_start_time_);
   compositor_frame_reporting_controller_->DidSubmitCompositorFrame(frame_token);
   submit_start_time_ = Now();
-  submit_ack_watchdog_enabled_ = true;
 }
 
 void CompositorTimingHistory::DidNotProduceFrame() {
@@ -937,8 +923,6 @@ void CompositorTimingHistory::DidReceiveCompositorFrameAck() {
   DCHECK_NE(base::TimeTicks(), submit_start_time_);
   base::TimeDelta submit_to_ack_duration = Now() - submit_start_time_;
   uma_reporter_->AddSubmitToAckLatency(submit_to_ack_duration);
-  if (submit_ack_watchdog_enabled_)
-    submit_ack_watchdog_enabled_ = false;
   submit_start_time_ = base::TimeTicks();
 }
 

cc/scheduler/compositor_timing_history.h

@@ -161,9 +161,6 @@ class CC_EXPORT CompositorTimingHistory {
 
   bool pending_tree_is_impl_side_;
 
-  // Watchdog timers.
-  bool submit_ack_watchdog_enabled_;
-
   std::unique_ptr<UMAReporter> uma_reporter_;
 
   // Owned by LayerTreeHost and is destroyed when LayerTreeHost is destroyed.