cc: Make BackToBackBeginFrameSource a SyntheticBeginFrameSource.

cc/scheduler/begin_frame_source_unittest.cc

Index: cc/scheduler/begin_frame_source_unittest.cc
diff --git a/cc/scheduler/begin_frame_source_unittest.cc b/cc/scheduler/begin_frame_source_unittest.cc
index fbeba81732aba029bdc6abf1db1a55d7c56080e3..a1151c7459b80692858acd36ea9b27d7ca2f44c1 100644
--- a/cc/scheduler/begin_frame_source_unittest.cc
+++ b/cc/scheduler/begin_frame_source_unittest.cc
@@ -173,42 +173,29 @@ TEST(BeginFrameSourceBaseTest, MultipleObservers) {
   source.RemoveObserver(&obs2);
 }
 
-// BackToBackBeginFrameSource testing -----------------------------------------
-class TestBackToBackBeginFrameSource : public BackToBackBeginFrameSource {
- public:
-  TestBackToBackBeginFrameSource(base::SimpleTestTickClock* now_src,
-                                 base::SingleThreadTaskRunner* task_runner)
-      : BackToBackBeginFrameSource(task_runner), now_src_(now_src) {}
-
- protected:
-  base::TimeTicks Now() override { return now_src_->NowTicks(); }
-
-  // Not owned.
-  base::SimpleTestTickClock* now_src_;
-};
-
 class BackToBackBeginFrameSourceTest : public ::testing::Test {
- public:
+ protected:
   static const int64_t kDeadline;
   static const int64_t kInterval;
 
-  std::unique_ptr<base::SimpleTestTickClock> now_src_;
-  scoped_refptr<OrderedSimpleTaskRunner> task_runner_;
-  std::unique_ptr<TestBackToBackBeginFrameSource> source_;
-  std::unique_ptr<MockBeginFrameObserver> obs_;
-
   void SetUp() override {
     now_src_.reset(new base::SimpleTestTickClock());
     now_src_->Advance(base::TimeDelta::FromMicroseconds(1000));
     task_runner_ =
         make_scoped_refptr(new OrderedSimpleTaskRunner(now_src_.get(), false));
-    source_.reset(
-        new TestBackToBackBeginFrameSource(now_src_.get(), task_runner_.get()));
-    obs_ =
-        base::WrapUnique(new ::testing::StrictMock<MockBeginFrameObserver>());
+    std::unique_ptr<TestDelayBasedTimeSource> time_source(
+        new TestDelayBasedTimeSource(now_src_.get(), task_runner_.get()));
+    source_.reset(new SyntheticBeginFrameSource(std::move(time_source)));
+    source_->SetUnthrottled(true);
+    obs_ = base::WrapUnique(new ::testing::StrictMock<MockBeginFrameObserver>);
   }
 
   void TearDown() override { obs_.reset(); }
+
+  std::unique_ptr<base::SimpleTestTickClock> now_src_;
+  scoped_refptr<OrderedSimpleTaskRunner> task_runner_;
+  std::unique_ptr<SyntheticBeginFrameSource> source_;
+  std::unique_ptr<MockBeginFrameObserver> obs_;
 };
 
 const int64_t BackToBackBeginFrameSourceTest::kDeadline =
@@ -240,6 +227,10 @@ TEST_F(BackToBackBeginFrameSourceTest,
   source_->RemoveObserver(obs_.get());
   source_->DidFinishFrame(obs_.get(), 0);
 
+  // Verify no BeginFrame is sent to |obs_|. There is a pending task in the
+  // task_runner_ as a BeginFrame was posted, but it gets aborted since |obs_|
+  // is removed.
+  task_runner_->RunPendingTasks();
   EXPECT_FALSE(task_runner_->HasPendingTasks());
 }
 
@@ -276,7 +267,9 @@ TEST_F(BackToBackBeginFrameSourceTest,
   source_->DidFinishFrame(obs_.get(), 0);
 
   now_src_->Advance(base::TimeDelta::FromMicroseconds(10));
-  EXPECT_BEGIN_FRAME_USED(*obs_, 1130, 1130 + kDeadline, kInterval);
+  // The begin frame is posted at the time when the observer was added,
+  // so it ignores changes to "now" afterward.
+  EXPECT_BEGIN_FRAME_USED(*obs_, 1110, 1110 + kDeadline, kInterval);
   EXPECT_TRUE(task_runner_->HasPendingTasks());
   task_runner_->RunPendingTasks();
 }
@@ -299,7 +292,9 @@ TEST_F(BackToBackBeginFrameSourceTest,
   source_->AddObserver(obs_.get());
 
   now_src_->Advance(base::TimeDelta::FromMicroseconds(10));
-  EXPECT_BEGIN_FRAME_USED(*obs_, 1130, 1130 + kDeadline, kInterval);
+  // Ticks at the time at which the observer was added, ignoring the
+  // last change to "now".
+  EXPECT_BEGIN_FRAME_USED(*obs_, 1120, 1120 + kDeadline, kInterval);
   EXPECT_TRUE(task_runner_->HasPendingTasks());
   task_runner_->RunPendingTasks();
 }
@@ -316,7 +311,12 @@ TEST_F(BackToBackBeginFrameSourceTest, DidFinishFrameRemainingFrames) {
   EXPECT_BEGIN_FRAME_SOURCE_PAUSED(*obs_, false);
   source_->AddObserver(obs_.get());
   EXPECT_BEGIN_FRAME_USED(*obs_, 1000, 1000 + kDeadline, kInterval);
+  // Runs the pending begin frame.
+  task_runner_->RunPendingTasks();
+  // While running the begin frame, the next frame was cancelled, this
+  // runs the next frame, sees it was cancelled, and goes to sleep.
   task_runner_->RunPendingTasks();
+  EXPECT_FALSE(task_runner_->HasPendingTasks());
 
   now_src_->Advance(base::TimeDelta::FromMicroseconds(100));
 
@@ -363,7 +363,9 @@ TEST_F(BackToBackBeginFrameSourceTest, DelayInPostedTaskProducesCorrectFrame) {
   now_src_->Advance(base::TimeDelta::FromMicroseconds(100));
   source_->DidFinishFrame(obs_.get(), 0);
   now_src_->Advance(base::TimeDelta::FromMicroseconds(50));
-  EXPECT_BEGIN_FRAME_USED(*obs_, 1150, 1150 + kDeadline, kInterval);
+  // Ticks at the time the last frame finished, so ignores the last change to
+  // "now".
+  EXPECT_BEGIN_FRAME_USED(*obs_, 1100, 1100 + kDeadline, kInterval);
 
   EXPECT_TRUE(task_runner_->HasPendingTasks());
   task_runner_->RunPendingTasks();
@@ -418,6 +420,9 @@ TEST_F(BackToBackBeginFrameSourceTest, MultipleObserversInterleaved) {
 
   source_->DidFinishFrame(&obs1, 0);
   source_->RemoveObserver(&obs1);
+  // Finishing the frame for |obs1| posts a begin frame task, which will be
+  // aborted since |obs1| is removed. Clear that from the task runner.
+  task_runner_->RunPendingTasks();
 
   now_src_->Advance(base::TimeDelta::FromMicroseconds(100));
   source_->DidFinishFrame(&obs2, 0);
@@ -428,12 +433,43 @@ TEST_F(BackToBackBeginFrameSourceTest, MultipleObserversInterleaved) {
   source_->RemoveObserver(&obs2);
 }
 
+TEST_F(BackToBackBeginFrameSourceTest, MultipleObserversAtOnce) {
+  StrictMock<MockBeginFrameObserver> obs1, obs2;
+
+  EXPECT_BEGIN_FRAME_SOURCE_PAUSED(obs1, false);
+  EXPECT_BEGIN_FRAME_SOURCE_PAUSED(obs2, false);
+  source_->AddObserver(&obs1);
+  source_->AddObserver(&obs2);
+  EXPECT_BEGIN_FRAME_USED(obs1, 1000, 1000 + kDeadline, kInterval);
+  EXPECT_BEGIN_FRAME_USED(obs2, 1000, 1000 + kDeadline, kInterval);
+  task_runner_->RunPendingTasks();
+
+  // |obs1| finishes first.
+  now_src_->Advance(base::TimeDelta::FromMicroseconds(100));
+  source_->DidFinishFrame(&obs1, 0);
+
+  // |obs2| finishes also, before getting to the newly posted begin frame.
+  now_src_->Advance(base::TimeDelta::FromMicroseconds(100));
+  source_->DidFinishFrame(&obs2, 0);
+
+  // Because the begin frame source already ticked when |obs1| finished,
+  // we see it as the frame time for both observers.
+  EXPECT_BEGIN_FRAME_USED(obs1, 1100, 1100 + kDeadline, kInterval);
+  EXPECT_BEGIN_FRAME_USED(obs2, 1100, 1100 + kDeadline, kInterval);
+  task_runner_->RunPendingTasks();
+
+  source_->DidFinishFrame(&obs1, 0);
+  source_->RemoveObserver(&obs1);
+  source_->DidFinishFrame(&obs2, 0);
+  source_->RemoveObserver(&obs2);
+}
+
 // SyntheticBeginFrameSource testing ------------------------------------------
 class SyntheticBeginFrameSourceTest : public ::testing::Test {
  public:
   std::unique_ptr<base::SimpleTestTickClock> now_src_;
   scoped_refptr<OrderedSimpleTaskRunner> task_runner_;
-  std::unique_ptr<TestSyntheticBeginFrameSource> source_;
+  std::unique_ptr<SyntheticBeginFrameSource> source_;
   std::unique_ptr<MockBeginFrameObserver> obs_;
 
   void SetUp() override {
@@ -441,10 +477,12 @@ class SyntheticBeginFrameSourceTest : public ::testing::Test {
     now_src_->Advance(base::TimeDelta::FromMicroseconds(1000));
     task_runner_ =
         make_scoped_refptr(new OrderedSimpleTaskRunner(now_src_.get(), false));
-    source_.reset(new TestSyntheticBeginFrameSource(
-        now_src_.get(), task_runner_.get(),
-        base::TimeDelta::FromMicroseconds(10000)));
-    obs_ = base::WrapUnique(new MockBeginFrameObserver());
+    std::unique_ptr<DelayBasedTimeSource> time_source(
+        new TestDelayBasedTimeSource(now_src_.get(), task_runner_.get()));
+    time_source->SetTimebaseAndInterval(
+        base::TimeTicks(), base::TimeDelta::FromMicroseconds(10000));
+    source_.reset(new SyntheticBeginFrameSource(std::move(time_source)));
+    obs_.reset(new MockBeginFrameObserver);
   }
 
   void TearDown() override { obs_.reset(); }