cc: Add scheduler support for invalidating content on impl thread.

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 91ae485850381b5ce41b3eb509a11d06deb5ba09..3e85448ee2a7f2140c731e560328576b71c67713 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -33,6 +33,7 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       draw_funnel_(false),
       send_begin_main_frame_funnel_(true),
       invalidate_compositor_frame_sink_funnel_(false),
+      impl_side_invalidation_funnel_(false),
       prepare_tiles_funnel_(0),
       consecutive_checkerboard_animations_(0),
       pending_submit_frames_(0),
@@ -60,7 +61,9 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       last_commit_had_no_updates_(false),
       wait_for_ready_to_draw_(false),
       did_draw_in_last_frame_(false),
-      did_submit_in_last_frame_(false) {}
+      did_submit_in_last_frame_(false),
+      needs_impl_side_invalidation_(false),
+      run_impl_side_invalidation_after_main_frame_aborted_(false) {}
 
 const char* SchedulerStateMachine::CompositorFrameSinkStateToString(
     CompositorFrameSinkState state) {
@@ -177,6 +180,8 @@ const char* SchedulerStateMachine::ActionToString(Action action) {
       return "ACTION_PREPARE_TILES";
     case ACTION_INVALIDATE_COMPOSITOR_FRAME_SINK:
       return "ACTION_INVALIDATE_COMPOSITOR_FRAME_SINK";
+    case ACTION_RUN_IMPL_SIDE_INVALIDATION:
+      return "ACTION_RUN_IMPL_SIDE_INVALIDATION";
   }
   NOTREACHED();
   return "???";
@@ -558,6 +563,8 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
     return ACTION_PREPARE_TILES;
   if (ShouldSendBeginMainFrame())
     return ACTION_SEND_BEGIN_MAIN_FRAME;
+  if (ShouldRunImplSideInvalidation())
+    return ACTION_RUN_IMPL_SIDE_INVALIDATION;
   if (ShouldInvalidateCompositorFrameSink())
     return ACTION_INVALIDATE_COMPOSITOR_FRAME_SINK;
   if (ShouldBeginCompositorFrameSinkCreation())
@@ -565,6 +572,79 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   return ACTION_NONE;
 }
 
+bool SchedulerStateMachine::ShouldRunImplSideInvalidation() const {
+  if (!needs_impl_side_invalidation_)
+    return false;
+
+  if (!CouldCreatePendingTree())
+    return false;
+
+  // If the main thread is ready to commit, the impl-side invalidations will be
+  // merged with the incoming main frame.
+  if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT)
+    return false;
+
+  // Don't invalidate too many times in the same frame.
+  if (impl_side_invalidation_funnel_)
+    return false;
+
+  // If invalidations go to the active tree and we are waiting for the previous
+  // frame to be drawn, submitted and acked.
+  if (settings_.commit_to_active_tree &&
+      (active_tree_needs_first_draw_ || IsDrawThrottled())) {
+    return false;
+  }
+
+  // Don't keep waiting on the main thread if the commits are being aborted.
+  if (run_impl_side_invalidation_after_main_frame_aborted_)
+    return true;
+
+  // If BeginMainFrame has been sent, let's wait for the main thread before
+  // pipelining impl-side invalidations.
+  // TODO(khushalsagar): If the main thread is high latency, may be run
+  // impl-side invalidations instead of waiting on the main thread?
+  if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_SENT ||
+      begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_STARTED)
+    return false;
+
+  // If a main frame request is pending, always prioritize sending a
+  // BeginMainFrame and receiving an update from the main thread before creating
+  // a pending tree for impl-side invalidations.
+  if (CouldSendBeginMainFrame() &&
+      begin_main_frame_state_ ==
+          BeginMainFrameState::BEGIN_MAIN_FRAME_STATE_IDLE)
+    return false;
+
+  // At this point, create a pending tree to run impl-side invalidations.
+  return true;
+}
+
+void SchedulerStateMachine::WillRunImplSideInvalidation() {
+  DCHECK(needs_impl_side_invalidation_);
+
+  needs_impl_side_invalidation_ = false;
+  has_pending_tree_ = true;
+  run_impl_side_invalidation_after_main_frame_aborted_ = false;
+  impl_side_invalidation_funnel_ = true;
+}
+
+bool SchedulerStateMachine::CouldCreatePendingTree() const {
+  // Can't create a new pending tree till the current one is activated.
+  if (has_pending_tree_)
+    return false;
+
+  // Can't make frames while we're invisible.
+  if (!visible_)
+    return false;
+
+  // If the BeginFrameSource is paused, we will not be able to make any impl
+  // frames.
+  if (begin_frame_source_paused_)
+    return false;
+
+  return true;
+}
+
 void SchedulerStateMachine::WillSendBeginMainFrame() {
   DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
   DCHECK(visible_);
@@ -589,6 +669,13 @@ void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
     has_pending_tree_ = true;
     pending_tree_is_ready_for_activation_ = false;
     wait_for_ready_to_draw_ = settings_.commit_to_active_tree;
+
+    // If there was a commit, the impl-side invalidations will be merged with
+    // it.
+    if (needs_impl_side_invalidation_)
+      WillRunImplSideInvalidation();

[brianderson, 2017/02/03 00:54:53]

I know it'll seem like extra boiler plate, but this is a little weird since the
Will* methods are usually called by cc::Scheduler. Can you add a shared method
that you call here and from WillRunImplSideInvalidation?

[Khushal, 2017/02/03 01:45:11]

Done.

+  } else if (needs_impl_side_invalidation_) {
+    run_impl_side_invalidation_after_main_frame_aborted_ = true;
   }
 
   // Update state related to forced draws.
@@ -689,6 +776,10 @@ void SchedulerStateMachine::DidDraw(DrawResult draw_result) {
   DidDrawInternal(draw_result);
 }
 
+void SchedulerStateMachine::SetNeedsImplSideInvalidation() {
+  needs_impl_side_invalidation_ = true;
+}
+
 void SchedulerStateMachine::AbortDraw() {
   // Pretend like the draw was successful.
   // Note: We may abort at any time and cannot DCHECK that
@@ -767,7 +858,8 @@ bool SchedulerStateMachine::BeginFrameRequiredForAction() const {
     return true;
 
   return needs_redraw_ || needs_one_begin_impl_frame_ ||
-         (needs_begin_main_frame_ && !defer_commits_);
+         (needs_begin_main_frame_ && !defer_commits_) ||
+         needs_impl_side_invalidation_;
 }
 
 // These are cases where we are very likely want a BeginFrame message in the
@@ -827,6 +919,7 @@ void SchedulerStateMachine::OnBeginImplFrame() {
   // Clear funnels for any actions we perform during the frame.
   send_begin_main_frame_funnel_ = false;
   invalidate_compositor_frame_sink_funnel_ = false;
+  impl_side_invalidation_funnel_ = false;
 
   // "Drain" the PrepareTiles funnel.
   if (prepare_tiles_funnel_ > 0)