Reland of cc: Remove frame queuing from the scheduler.

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 800f4131779189e3e5da873f3fe735f11405e59a..ecc131b434c75ac0bd03994bdf62503381807b22 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -123,10 +123,6 @@ const char* SchedulerStateMachine::BeginMainFrameStateToString(
       return "BEGIN_MAIN_FRAME_STATE_STARTED";
     case BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT:
       return "BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT";
-    case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION:
-      return "BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION";
-    case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW:
-      return "BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW";
   }
   NOTREACHED();
   return "???";
@@ -367,6 +363,9 @@ bool SchedulerStateMachine::ShouldDraw() const {
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
     return false;
 
+  if (wait_for_ready_to_draw_)
+    return false;
+
   // Only handle forced redraws due to timeouts on the regular deadline.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     return true;
@@ -429,6 +428,16 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE)
     return false;
 
+  // MFBA is disabled and we are waiting for previous activation.
+  if (!settings_.main_frame_before_activation_enabled && has_pending_tree_)
+    return false;
+
+  // We are waiting for previous frame to be drawn, swapped and acked.
+  if (settings_.commit_to_active_tree &&
+      (active_tree_needs_first_draw_ || SwapThrottled())) {
+    return false;
+  }
+
   // Don't send BeginMainFrame early if we are prioritizing the active tree
   // because of ImplLatencyTakesPriority.
   if (ImplLatencyTakesPriority() &&
@@ -484,6 +493,11 @@ bool SchedulerStateMachine::ShouldCommit() const {
     return false;
   }
 
+  // Active tree resources might still be in use until the Display draws.
+  // if (settings_.commit_to_active_tree && SwapThrottled())

[enne (OOO), 2016/09/22 19:01:47]

Leftover code?

[sunnyps, 2016/09/24 01:15:02]

Removed.

+  // return false;
+  DCHECK(!settings_.commit_to_active_tree || !SwapThrottled());

[enne (OOO), 2016/09/22 19:01:47]

It's nice to DCHECK this.

[sunnyps, 2016/09/24 01:15:02]

Yes, although this crashes when we have pure impl-side draws.

+
   // If we only have an active tree, it is incorrect to replace it
   // before we've drawn it.
   DCHECK(!settings_.commit_to_active_tree || !active_tree_needs_first_draw_);
@@ -566,12 +580,7 @@ void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
           commit_has_no_updates));
   commit_count_++;
   last_commit_had_no_updates_ = commit_has_no_updates;
-
-  if (commit_has_no_updates || settings_.main_frame_before_activation_enabled) {
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
-  } else {
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION;
-  }
+  begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 
   if (!commit_has_no_updates) {
     // Pending tree only exists if commit had updates.
@@ -597,13 +606,6 @@ void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
 }
 
 void SchedulerStateMachine::WillActivate() {
-  if (begin_main_frame_state_ ==
-      BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION) {
-    begin_main_frame_state_ = settings_.commit_to_active_tree
-                                  ? BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW
-                                  : BEGIN_MAIN_FRAME_STATE_IDLE;
-  }
-
   if (compositor_frame_sink_state_ ==
       COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_ACTIVATION)
     compositor_frame_sink_state_ = COMPOSITOR_FRAME_SINK_ACTIVE;
@@ -636,9 +638,6 @@ void SchedulerStateMachine::WillDrawInternal() {
 
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
-
-  if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW)
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 }
 
 void SchedulerStateMachine::DidDrawInternal(DrawResult draw_result) {
@@ -729,8 +728,7 @@ void SchedulerStateMachine::WillInvalidateCompositorFrameSink() {
 }
 
 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
-  TRACE_EVENT_INSTANT0("cc",
-                       "Scheduler: SkipNextBeginMainFrameToReduceLatency",
+  TRACE_EVENT_INSTANT0("cc", "Scheduler: SkipNextBeginMainFrameToReduceLatency",
                        TRACE_EVENT_SCOPE_THREAD);
   skip_next_begin_main_frame_to_reduce_latency_ = true;
 }
@@ -953,9 +951,13 @@ void SchedulerStateMachine::SetResourcelessSoftwareDraw(
   resourceless_draw_ = resourceless_draw;
 }
 
-void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
+void SchedulerStateMachine::SetCanDraw(bool can_draw) {
+  can_draw_ = can_draw;
+}
 
-void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
+void SchedulerStateMachine::SetNeedsRedraw() {
+  needs_redraw_ = true;
+}
 
 bool SchedulerStateMachine::OnlyImplSideUpdatesExpected() const {
   bool has_impl_updates = needs_redraw_ || needs_one_begin_impl_frame_;
@@ -1029,11 +1031,6 @@ void SchedulerStateMachine::NotifyReadyToCommit() {
   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_STARTED)
       << AsValue()->ToString();
   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT;
-  // In commit_to_active_tree mode, commit should happen right after
-  // BeginFrame, meaning when this function is called, next action should be
-  // commit.
-  if (settings_.commit_to_active_tree)
-    DCHECK(ShouldCommit());
 }
 
 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {