Make DefaultEstimatedParentDrawTime take into account vsync interval

Rather than hard-coding the estimated draw time, calculate it from the
BeginFrame interval.

Change-Id: I5fc7494d5c08cf8ef84a55f1c672c173caf75bd0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529621
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: Eric Karl <ericrk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642308}

components/viz/common/frame_sinks/begin_frame_args.h

@@ -86,14 +86,18 @@ struct VIZ_COMMON_EXPORT BeginFrameArgs {
     return base::TimeDelta::FromMicroseconds(16666);
   }
 
-  // This is a hard-coded deadline adjustment that assumes 60Hz, to be used in
-  // cases where a good estimated draw time is not known. Using 1/3 of the vsync
-  // as the default adjustment gives the Browser the last 1/3 of a frame to
-  // produce output, the Renderer Impl thread the middle 1/3 of a frame to
-  // produce ouput, and the Renderer Main thread the first 1/3 of a frame to
-  // produce output.
-  static constexpr base::TimeDelta DefaultEstimatedParentDrawTime() {
-    return base::TimeDelta::FromMicroseconds(16666 / 3);
+  // This is a hard-coded deadline adjustment used by the display compositor.
+  // Using 1/3 of the vsync as the default adjustment gives the display
+  // compositor the last 1/3 of a frame to produce output, the client impl
+  // thread the middle 1/3 of a frame to produce output, and the client's main
+  // thread the first 1/3 of a frame to produce output.
+  static constexpr float kDefaultEstimatedDisplayDrawTimeRatio = 1.f / 3;
+
+  // Returns how much time the display should reserve for draw and swap if the
+  // BeginFrame interval is |interval|.
+  static base::TimeDelta DefaultEstimatedDisplayDrawTime(
+      base::TimeDelta interval) {
+    return interval * kDefaultEstimatedDisplayDrawTimeRatio;
   }
 
   bool IsValid() const { return interval >= base::TimeDelta(); }

components/viz/service/display/display_scheduler.cc

@@ -259,7 +259,7 @@ bool DisplayScheduler::OnBeginFrameDerivedImpl(const BeginFrameArgs& args) {
   // Schedule the deadline.
   current_begin_frame_args_ = save_args;
   current_begin_frame_args_.deadline -=
-      BeginFrameArgs::DefaultEstimatedParentDrawTime();
+      BeginFrameArgs::DefaultEstimatedDisplayDrawTime(save_args.interval);
   inside_begin_frame_deadline_interval_ = true;
   UpdateHasPendingSurfaces();
   ScheduleBeginFrameDeadline();

components/viz/service/display/display_scheduler_unittest.cc

@@ -687,7 +687,8 @@ TEST_F(DisplaySchedulerTest, DidSwapBuffers) {
   AdvanceTimeAndBeginFrameForTest({sid2});
   base::TimeTicks expected_deadline =
       scheduler_.LastUsedBeginFrameArgs().deadline -
-      BeginFrameArgs::DefaultEstimatedParentDrawTime();
+      BeginFrameArgs::DefaultEstimatedDisplayDrawTime(
+          scheduler_.LastUsedBeginFrameArgs().interval);
   EXPECT_EQ(expected_deadline,
             scheduler_.DesiredBeginFrameDeadlineTimeForTest());
   // Still waiting for surface 2. Once it updates, deadline should trigger

components/viz/test/begin_frame_args_test.cc

@@ -28,7 +28,8 @@ BeginFrameArgs CreateBeginFrameArgsForTesting(
   return BeginFrameArgs::Create(
       location, source_id, sequence_number, frame_time,
       frame_time + BeginFrameArgs::DefaultInterval() -
-          BeginFrameArgs::DefaultEstimatedParentDrawTime(),
+          BeginFrameArgs::DefaultEstimatedDisplayDrawTime(
+              BeginFrameArgs::DefaultInterval()),
       BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL);
 }
 
@@ -70,7 +71,8 @@ BeginFrameArgs CreateBeginFrameArgsForTesting(
   return BeginFrameArgs::Create(
       location, source_id, sequence_number, now,
       now + BeginFrameArgs::DefaultInterval() -
-          BeginFrameArgs::DefaultEstimatedParentDrawTime(),
+          BeginFrameArgs::DefaultEstimatedDisplayDrawTime(
+              BeginFrameArgs::DefaultInterval()),
       BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL);
 }