cc: Aggressively expire retro frames.

If we're not aggressive about expiring a retro frame (e.g. MISSED frames)
then it's possible to enter a high latency mode often.

BUG=469953

Review URL: https://codereview.chromium.org/1055113004

Cr-Commit-Position: refs/heads/master@{#330465}

cc/scheduler/scheduler.cc

@@ -434,7 +434,7 @@ void Scheduler::BeginRetroFrame() {
 
   while (!begin_retro_frame_args_.empty()) {
     const BeginFrameArgs& args = begin_retro_frame_args_.front();
-    base::TimeTicks expiration_time = args.frame_time + args.interval;
+    base::TimeTicks expiration_time = args.deadline;
     if (now <= expiration_time)
       break;
     TRACE_EVENT_INSTANT2(

cc/scheduler/scheduler_unittest.cc

@@ -400,13 +400,15 @@ class SchedulerTest : public testing::Test {
     }
   }
 
-  void SendNextBeginFrame() {
+  BeginFrameArgs SendNextBeginFrame() {
     DCHECK(scheduler_->settings().use_external_begin_frame_source);
     // Creep the time forward so that any BeginFrameArgs is not equal to the
     // last one otherwise we violate the BeginFrameSource contract.
     now_src_->AdvanceNow(BeginFrameArgs::DefaultInterval());
-    fake_external_begin_frame_source_->TestOnBeginFrame(
-        CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src()));
+    BeginFrameArgs args =
+        CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
+    fake_external_begin_frame_source_->TestOnBeginFrame(args);
+    return args;
   }
 
   FakeExternalBeginFrameSource* fake_external_begin_frame_source() const {
@@ -1606,7 +1608,7 @@ TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooEarly) {
   scheduler_->NotifyBeginMainFrameStarted();
 
   client_->Reset();
-  SendNextBeginFrame();
+  BeginFrameArgs retro_frame_args = SendNextBeginFrame();
   // This BeginFrame is queued up as a retro frame.
   EXPECT_NO_ACTION(client_);
   // The previous deadline is still pending.
@@ -1630,10 +1632,8 @@ TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooEarly) {
   scheduler_->SetNeedsRedraw();
   EXPECT_NO_ACTION(client_);
 
-  // Let's advance sufficiently past the next frame's deadline.
-  now_src()->AdvanceNow(BeginFrameArgs::DefaultInterval() -
-                        BeginFrameArgs::DefaultEstimatedParentDrawTime() +
-                        base::TimeDelta::FromMicroseconds(1));
+  // Let's advance to the retro frame's deadline.
+  now_src()->AdvanceNow(retro_frame_args.deadline - now_src()->Now());
 
   // The retro frame hasn't expired yet.
   task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(false));
@@ -1648,7 +1648,7 @@ TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooEarly) {
   EXPECT_SINGLE_ACTION("ScheduledActionDrawAndSwapIfPossible", client_);
 }
 
-TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooLate) {
+TEST_F(SchedulerTest, RetroFrameExpiresOnTime) {
   scheduler_settings_.use_external_begin_frame_source = true;
   SetUpScheduler(true);
 
@@ -1666,7 +1666,7 @@ TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooLate) {
   scheduler_->NotifyBeginMainFrameStarted();
 
   client_->Reset();
-  SendNextBeginFrame();
+  BeginFrameArgs retro_frame_args = SendNextBeginFrame();
   // This BeginFrame is queued up as a retro frame.
   EXPECT_NO_ACTION(client_);
   // The previous deadline is still pending.
@@ -1690,14 +1690,64 @@ TEST_F(SchedulerTest, RetroFrameDoesNotExpireTooLate) {
   scheduler_->SetNeedsRedraw();
   EXPECT_NO_ACTION(client_);
 
-  // Let's advance sufficiently past the next frame's deadline.
-  now_src()->AdvanceNow(BeginFrameArgs::DefaultInterval() +
+  // Let's advance sufficiently past the retro frame's deadline.
+  now_src()->AdvanceNow(retro_frame_args.deadline - now_src()->Now() +
                         base::TimeDelta::FromMicroseconds(1));
 
   // The retro frame should've expired.
   EXPECT_NO_ACTION(client_);
 }
 
+TEST_F(SchedulerTest, MissedFrameDoesNotExpireTooEarly) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(client_->needs_begin_frames());
+  EXPECT_SINGLE_ACTION("SetNeedsBeginFrames(true)", client_);
+
+  BeginFrameArgs missed_frame_args =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
+  missed_frame_args.type = BeginFrameArgs::MISSED;
+
+  // Advance to the deadline.
+  now_src()->AdvanceNow(missed_frame_args.deadline - now_src()->Now());
+
+  // Missed frame is handled because it's on time.
+  client_->Reset();
+  fake_external_begin_frame_source_->TestOnBeginFrame(missed_frame_args);
+  EXPECT_TRUE(
+      task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(false)));
+  EXPECT_ACTION("WillBeginImplFrame", client_, 0, 2);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 1, 2);
+  EXPECT_TRUE(scheduler_->BeginImplFrameDeadlinePending());
+}
+
+TEST_F(SchedulerTest, MissedFrameExpiresOnTime) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(client_->needs_begin_frames());
+  EXPECT_SINGLE_ACTION("SetNeedsBeginFrames(true)", client_);
+
+  BeginFrameArgs missed_frame_args =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
+  missed_frame_args.type = BeginFrameArgs::MISSED;
+
+  // Advance sufficiently past the deadline.
+  now_src()->AdvanceNow(missed_frame_args.deadline - now_src()->Now() +
+                        base::TimeDelta::FromMicroseconds(1));
+
+  // Missed frame is dropped because it's too late.
+  client_->Reset();
+  fake_external_begin_frame_source_->TestOnBeginFrame(missed_frame_args);
+  EXPECT_FALSE(
+      task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(false)));
+  EXPECT_NO_ACTION(client_);
+  EXPECT_FALSE(scheduler_->BeginImplFrameDeadlinePending());
+}
+
 void SchedulerTest::BeginFramesNotFromClient(
     bool use_external_begin_frame_source,
     bool throttle_frame_production) {