Revert of cc: Remove frame queuing from the scheduler.

cc/scheduler/scheduler_state_machine_unittest.cc

Index: cc/scheduler/scheduler_state_machine_unittest.cc
diff --git a/cc/scheduler/scheduler_state_machine_unittest.cc b/cc/scheduler/scheduler_state_machine_unittest.cc
index 4a16da23a40bc0bf42e94325addd9a632880f7c6..7f28395a8310a657c04929e7df181c70831811b4 100644
--- a/cc/scheduler/scheduler_state_machine_unittest.cc
+++ b/cc/scheduler/scheduler_state_machine_unittest.cc
@@ -35,18 +35,18 @@
   EXPECT_ENUM_EQ(ActionToString, expected, state.NextAction()) \
       << state.AsValue()->ToString()
 
-#define EXPECT_ACTION_UPDATE_STATE(action)                                 \
-  EXPECT_ACTION(action);                                                   \
-  if (action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE || \
-      action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_FORCED) {      \
-    EXPECT_IMPL_FRAME_STATE(                                               \
-        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE);    \
-  }                                                                        \
-  PerformAction(&state, action);                                           \
-  if (action == SchedulerStateMachine::ACTION_NONE) {                      \
-    if (state.begin_impl_frame_state() ==                                  \
-        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)     \
-      state.OnBeginImplFrameIdle();                                        \
+#define EXPECT_ACTION_UPDATE_STATE(action)                                  \
+  EXPECT_ACTION(action);                                                    \
+  if (action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE ||  \
+      action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_FORCED) {       \
+    EXPECT_IMPL_FRAME_STATE(                                                \
+        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE);     \
+  }                                                                         \
+  PerformAction(&state, action);                                            \
+  if (action == SchedulerStateMachine::ACTION_NONE) {                       \
+    if (state.begin_impl_frame_state() ==                                   \
+        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)      \
+      state.OnBeginImplFrameIdle();                                         \
   }
 
 #define SET_UP_STATE(state)                                                \
@@ -62,17 +62,17 @@
 namespace {
 
 const SchedulerStateMachine::BeginImplFrameState all_begin_impl_frame_states[] =
-    {
-        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE,
-        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME,
-        SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE,
-};
+    {SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE,
+     SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME,
+     SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE, };
 
 const SchedulerStateMachine::BeginMainFrameState begin_main_frame_states[] = {
     SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE,
     SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT,
     SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_STARTED,
-    SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT};
+    SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT,
+    SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION,
+    SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW};
 
 // Exposes the protected state fields of the SchedulerStateMachine for testing
 class StateMachine : public SchedulerStateMachine {
@@ -1112,55 +1112,60 @@
   state.NotifyReadyToCommit();
   EXPECT_MAIN_FRAME_STATE(
       SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT);
+
   // Commit.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
-  // Commit always calls NotifyReadyToActivate in this mode.
+
+  // Now commit should wait for activation.
+  EXPECT_MAIN_FRAME_STATE(
+      SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION);
+
+  // No activation yet, so this commit is not drawn yet. Force to draw this
+  // frame, and still block BeginMainFrame.
+  state.SetNeedsRedraw(true);
+  state.SetNeedsBeginMainFrame();
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Cannot BeginMainFrame yet since last commit is not yet activated and drawn.
+  state.OnBeginImplFrame();
+  EXPECT_MAIN_FRAME_STATE(
+      SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Now activate sync tree.
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // No draw because we haven't received NotifyReadyToDraw yet.
-  state.OnBeginImplFrameDeadline();
   EXPECT_TRUE(state.active_tree_needs_first_draw());
   EXPECT_TRUE(state.needs_redraw());
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // Can't BeginMainFrame yet since last commit hasn't been drawn yet.
-  state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // Now call ready to draw which will allow the draw to happen and
-  // BeginMainFrame to be sent.
-  state.NotifyReadyToDraw();
-  state.OnBeginImplFrameDeadline();
-  EXPECT_ACTION_UPDATE_STATE(
-      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
-  // Swap throttled from this point.
+  EXPECT_MAIN_FRAME_STATE(
+      SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW);
+
+  // Swap throttled. Do not draw.
   state.DidSwapBuffers();
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // Can't BeginMainFrame yet since we're swap throttled.
-  state.OnBeginImplFrame();
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // Swap ack unblocks BeginMainFrame.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.DidSwapBuffersComplete();
-  EXPECT_ACTION_UPDATE_STATE(
-      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
-  state.NotifyBeginMainFrameStarted();
-  state.NotifyReadyToCommit();
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
-  state.NotifyReadyToActivate();
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-
-  // Draw the newly activated tree.
-  state.NotifyReadyToDraw();
-  state.OnBeginImplFrameDeadline();
-  EXPECT_ACTION_UPDATE_STATE(
-      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
-  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Haven't draw since last commit, do not begin new main frame.
+  state.OnBeginImplFrame();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // At BeginImplFrame deadline, draw. This draws unblocks BeginMainFrame.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
+  state.DidSwapBuffers();
+  state.DidSwapBuffersComplete();
+
+  // Now will be able to start main frame.
+  EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
+  EXPECT_FALSE(state.needs_redraw());
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, TestFullCycleWithCommitRequestInbetween) {