Scheduler: Switch from high to low latency mode if possible.

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 0fd0f57b3b25b8466f8479c933ac10c89db314a7..9b1a93056301579c828cd4a7c073ea8e863b1a45 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -41,7 +41,8 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       active_tree_needs_first_draw_(false),
       draw_if_possible_failed_(false),
       did_create_and_initialize_first_output_surface_(false),
-      smoothness_takes_priority_(false) {}
+      smoothness_takes_priority_(false),
+      skip_begin_main_frame_(false) {}
 
 const char* SchedulerStateMachine::OutputSurfaceStateToString(
     OutputSurfaceState state) {
@@ -259,6 +260,8 @@ scoped_ptr<base::Value> SchedulerStateMachine::AsValue() const  {
                           did_create_and_initialize_first_output_surface_);
   minor_state->SetBoolean("smoothness_takes_priority",
                           smoothness_takes_priority_);
+  minor_state->SetBoolean("skip_begin_main_frame",
+                          skip_begin_main_frame_);
   state->Set("minor_state", minor_state.release());
 
   return state.PassAs<base::Value>();
@@ -485,6 +488,9 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!HasInitializedOutputSurface())
     return false;
 
+  if (skip_begin_main_frame_)
+    return false;
+
   return true;
 }
 
@@ -756,6 +762,10 @@ void SchedulerStateMachine::SetMainThreadNeedsLayerTextures() {
   main_thread_needs_layer_textures_ = true;
 }
 
+void SchedulerStateMachine::SetSkipBeginMainFrame(bool skip) {
+  skip_begin_main_frame_ = skip;
+}
+
 bool SchedulerStateMachine::BeginImplFrameNeeded() const {
   // Proactive BeginImplFrames are bad for the synchronous compositor because we
   // have to draw when we get the BeginImplFrame and could end up drawing many
@@ -919,6 +929,19 @@ bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineEarly() const {
   return false;
 }
 
+bool SchedulerStateMachine::InHighLatencyMode() const {
+  if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
+    return false;
+
+  if (commit_state_ != COMMIT_STATE_IDLE)
+    return true;
+
+  if (active_tree_needs_first_draw_ || has_pending_tree_ )

[brianderson, 2013/11/01 00:22:59]

Can you split this condition into separate if statements and add a comment above
each condition explaining why we are in a high latency mode?

+    return true;
+
+  return false;
+}
+
 void SchedulerStateMachine::DidEnterPollForAnticipatedDrawTriggers() {
   current_frame_number_++;
   inside_poll_for_anticipated_draw_triggers_ = true;