Unified BeginFrame scheduling

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 723c40c80c276d42ce3d1e2df2c58f51dfad5742..fe291ed46b9d941092e3e8edee45e7fc9f0f6085 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -47,7 +47,8 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       smoothness_takes_priority_(false),
       skip_next_begin_main_frame_to_reduce_latency_(false),
       skip_begin_main_frame_to_reduce_latency_(false),
-      continuous_painting_(false) {
+      continuous_painting_(false),
+      children_need_begin_frames_(false) {
 }
 
 const char* SchedulerStateMachine::OutputSurfaceStateToString(
@@ -704,10 +705,14 @@ bool SchedulerStateMachine::BeginFrameNeeded() const {
   // duplicate frames if our new frame isn't ready in time.
   // To poll for state with the synchronous compositor without having to draw,
   // we rely on ShouldPollForAnticipatedDrawTriggers instead.
-  if (!SupportsProactiveBeginFrame())
+  if (!SupportsProactiveBeginFrame()) {
+    DCHECK(!BeginFrameNeededToChildren());

[brianderson, 2014/09/04 18:45:46]

Can you add a comment regarding why we added this DCHECK?

     return BeginFrameNeededToAnimateOrDraw();
+  }
 
-  return BeginFrameNeededToAnimateOrDraw() || ProactiveBeginFrameWanted();
+  return (BeginFrameNeededToAnimateOrDraw() ||
+          BeginFrameNeededToChildren() ||
+          ProactiveBeginFrameWanted());
 }
 
 bool SchedulerStateMachine::ShouldPollForAnticipatedDrawTriggers() const {
@@ -733,6 +738,14 @@ bool SchedulerStateMachine::SupportsProactiveBeginFrame() const {
   return !settings_.using_synchronous_renderer_compositor;
 }
 
+void SchedulerStateMachine::SetChildrenNeedBeginFrames(
+    bool children_need_begin_frames) {
+#if !defined(OS_ANDROID) && !defined(OS_MACOSX)

[brianderson, 2014/09/04 18:45:46]

We try to avoid platforms-specific defines in cc if possible.
Maybe just DCHECK(settings_.begin_frame_publisher) for all platforms?

+  DCHECK(settings_.begin_frame_publisher && !settings_.begin_frame_receiver);
+#endif
+  children_need_begin_frames_ = children_need_begin_frames;
+}
+
 // These are the cases where we definitely (or almost definitely) have a
 // new frame to animate and/or draw and can draw.
 bool SchedulerStateMachine::BeginFrameNeededToAnimateOrDraw() const {
@@ -766,6 +779,17 @@ bool SchedulerStateMachine::BeginFrameNeededToAnimateOrDraw() const {
   return needs_redraw_;
 }
 
+bool SchedulerStateMachine::BeginFrameNeededToChildren() const {
+  if (!HasInitializedOutputSurface())
+    return false;
+
+  // If we can't draw, don't tick until we are notified that we can draw again.
+  if (!can_draw_)
+    return false;
+
+  return children_need_begin_frames_;
+}
+
 // These are cases where we are very likely to draw soon, but might not
 // actually have a new frame to draw when we receive the next BeginImplFrame.
 // Proactively requesting the BeginImplFrame helps hide the round trip latency