Revert of Revert "cc: Make scheduler run incoming frame after previous deadline."

cc/scheduler/scheduler_unittest.cc

Index: cc/scheduler/scheduler_unittest.cc
diff --git a/cc/scheduler/scheduler_unittest.cc b/cc/scheduler/scheduler_unittest.cc
index 72e31f537359a3315308a014740cababa0e09afd..82446ad72204d04d6600419978869d0f8d37434f 100644
--- a/cc/scheduler/scheduler_unittest.cc
+++ b/cc/scheduler/scheduler_unittest.cc
@@ -397,9 +397,13 @@
     // it will be already in the task queue.
     if (scheduler_->begin_frame_source() ==
         fake_external_begin_frame_source_.get()) {
+      // Run pending task for previous deadline first.
+      task_runner_->RunPendingTasks();
       EXPECT_TRUE(scheduler_->begin_frames_expected());
       SendNextBeginFrame();
     } else {
+      // Begin frame might be queued up and posted after the previous deadline
+      // runs so run tasks until we get to the next frame.
       task_runner_->RunTasksWhile(client_->FrameHasNotAdvancedCallback());
     }
   }
@@ -3510,10 +3514,11 @@
   client_->Reset();
 
   // Send the next BeginFrame before the previous one's deadline was executed.
-  // This should trigger the previous BeginFrame's deadline synchronously,
-  // during which tiles will be prepared. As a result of that, no further
-  // BeginFrames will be needed, and the new BeginFrame should be dropped.
+  // This will wait for the previous deadline after which no further BeginFrames
+  // will be needed, and the new BeginFrame should be dropped.
   BeginFrameArgs args = SendNextBeginFrame();
+
+  task_runner().RunPendingTasks();  // Run posted deadline.
   EXPECT_ACTION("ScheduledActionPrepareTiles", client_, 0, 3);
   EXPECT_ACTION("RemoveObserver(this)", client_, 1, 3);
   EXPECT_ACTION("SendBeginMainFrameNotExpectedSoon", client_, 2, 3);
@@ -3680,5 +3685,60 @@
       fake_external_begin_frame_source_->LastAckForObserver(scheduler_.get()));
 }
 
+TEST_F(SchedulerTest, BeginFrameWhilePreviousDeadlinePending) {
+  SetUpScheduler(EXTERNAL_BFS);
+
+  scheduler_->SetNeedsRedraw();
+
+  client_->Reset();
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_SINGLE_ACTION("WillBeginImplFrame", client_);
+
+  // Do not run pending deadline but send a new begin frame. The begin frame is
+  // saved and run when the previous frame is over.
+  client_->Reset();
+  SendNextBeginFrame();
+  EXPECT_NO_ACTION(client_);
+
+  task_runner_->RunPendingTasks();
+  EXPECT_SINGLE_ACTION("ScheduledActionDrawIfPossible", client_);
+
+  // The saved begin frame is posted as a task.
+  client_->Reset();
+  task_runner_->RunPendingTasks();
+  EXPECT_SINGLE_ACTION("WillBeginImplFrame", client_);
+}
+
+TEST_F(SchedulerTest, IncomingBeginFrameReplacesSavedBeginFrame) {
+  SetUpScheduler(EXTERNAL_BFS);
+
+  scheduler_->SetNeedsRedraw();
+
+  client_->Reset();
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_SINGLE_ACTION("WillBeginImplFrame", client_);
+
+  // Send two BeginFrames while deadline is pending.
+  client_->Reset();
+  SendNextBeginFrame();
+  EXPECT_NO_ACTION(client_);
+
+  SendNextBeginFrame();
+  EXPECT_NO_ACTION(client_);
+
+  task_runner_->RunPendingTasks();
+  EXPECT_SINGLE_ACTION("ScheduledActionDrawIfPossible", client_);
+
+  // Only the last BeginFrame runs.
+  client_->Reset();
+  task_runner_->RunPendingTasks();
+  EXPECT_SINGLE_ACTION("WillBeginImplFrame", client_);
+
+  client_->Reset();
+  task_runner_->RunPendingTasks();
+  EXPECT_ACTION("RemoveObserver(this)", client_, 0, 2);
+  EXPECT_ACTION("SendBeginMainFrameNotExpectedSoon", client_, 1, 2);
+}
+
 }  // namespace
 }  // namespace cc