cc: Add MainAndImplFrameTimeDelta UMA.

cc/scheduler/compositor_timing_history.cc

Index: cc/scheduler/compositor_timing_history.cc
diff --git a/cc/scheduler/compositor_timing_history.cc b/cc/scheduler/compositor_timing_history.cc
index f3ac0670525bd31d389c2008aebfd5c743649364..478d5f86b62109040beb44d9914ebd1b2d8dc981 100644
--- a/cc/scheduler/compositor_timing_history.cc
+++ b/cc/scheduler/compositor_timing_history.cc
@@ -50,6 +50,9 @@ class CompositorTimingHistory::UMAReporter {
                                base::TimeDelta estimate,
                                bool affects_estimate) = 0;
   virtual void AddSwapToAckLatency(base::TimeDelta duration) = 0;
+
+  // Synchronization measurements
+  virtual void AddMainAndImplSynchronized(bool synchronized);
 };
 
 namespace {
@@ -216,6 +219,11 @@ class RendererUMAReporter : public CompositorTimingHistory::UMAReporter {
     UMA_HISTOGRAM_CUSTOM_TIMES_MICROS("Scheduling.Renderer.SwapToAckLatency",
                                       duration);
   }
+
+  void AddMainAndImplSynchronized(bool synchronized) override {
+    UMA_HISTOGRAM_BOOLEAN("Scheduling.Renderer.MainAndImplSynchronized",
+                          synchronized);
+  }
 };
 
 class BrowserUMAReporter : public CompositorTimingHistory::UMAReporter {
@@ -297,6 +305,11 @@ class BrowserUMAReporter : public CompositorTimingHistory::UMAReporter {
     UMA_HISTOGRAM_CUSTOM_TIMES_MICROS("Scheduling.Browser.SwapToAckLatency",
                                       duration);
   }
+
+  void AddMainAndImplSynchronized(bool synchronized) override {
+    UMA_HISTOGRAM_BOOLEAN("Scheduling.Browser.MainAndImplSynchronized",
+                          synchronized);
+  }
 };
 
 class NullUMAReporter : public CompositorTimingHistory::UMAReporter {
@@ -331,6 +344,7 @@ class NullUMAReporter : public CompositorTimingHistory::UMAReporter {
                        base::TimeDelta estimate,
                        bool affects_estimate) override {}
   void AddSwapToAckLatency(base::TimeDelta duration) override {}
+  void AddMainAndImplSynchronized(bool synchronized) override {}
 };
 
 }  // namespace
@@ -658,7 +672,8 @@ void CompositorTimingHistory::WillDraw() {
   draw_start_time_ = Now();
 }
 
-void CompositorTimingHistory::DidDraw(bool used_new_active_tree) {
+void CompositorTimingHistory::DidDraw(bool used_new_active_tree,
+                                      bool main_thread_missed_last_deadline) {
   DCHECK_NE(base::TimeTicks(), draw_start_time_);
   base::TimeTicks draw_end_time = Now();
   base::TimeDelta draw_duration = draw_end_time - draw_start_time_;
@@ -683,13 +698,17 @@ void CompositorTimingHistory::DidDraw(bool used_new_active_tree) {
   }
   draw_end_time_prev_ = draw_end_time;
 
-  if (begin_main_frame_committing_continuously_ && used_new_active_tree) {
-    if (!new_active_tree_draw_end_time_prev_.is_null()) {
-      base::TimeDelta draw_interval =
-          draw_end_time - new_active_tree_draw_end_time_prev_;
-      uma_reporter_->AddCommitInterval(draw_interval);
+  if (used_new_active_tree) {
+    uma_reporter_->AddMainAndImplSynchronized(
+        !main_thread_missed_last_deadline);
+    if (begin_main_frame_committing_continuously_) {
+      if (!new_active_tree_draw_end_time_prev_.is_null()) {
+        base::TimeDelta draw_interval =
+            draw_end_time - new_active_tree_draw_end_time_prev_;
+        uma_reporter_->AddCommitInterval(draw_interval);
+      }
+      new_active_tree_draw_end_time_prev_ = draw_end_time;
     }
-    new_active_tree_draw_end_time_prev_ = draw_end_time;
   }
 
   draw_start_time_ = base::TimeTicks();