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..93e38bae634c804c70a25452f1c0cf1e5aa3b08b 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),
+      impl_side_invalidations_take_priority_(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_PERFORM_IMPL_SIDE_INVALIDATION:
+      return "ACTION_PERFORM_IMPL_SIDE_INVALIDATION";
   }
   NOTREACHED();
   return "???";
@@ -220,6 +225,8 @@ void SchedulerStateMachine::AsValueInto(
   state->SetInteger("funnel: prepare_tiles_funnel", prepare_tiles_funnel_);
   state->SetBoolean("funnel: invalidate_compositor_frame_sink_funnel",
                     invalidate_compositor_frame_sink_funnel_);
+  state->SetBoolean("funnel: impl_side_invalidation_funnel",
+                    impl_side_invalidation_funnel_);
   state->SetInteger("consecutive_checkerboard_animations",
                     consecutive_checkerboard_animations_);
   state->SetInteger("pending_submit_frames_", pending_submit_frames_);
@@ -255,6 +262,10 @@ void SchedulerStateMachine::AsValueInto(
   state->SetBoolean("last_commit_had_no_updates", last_commit_had_no_updates_);
   state->SetBoolean("did_draw_in_last_frame", did_draw_in_last_frame_);
   state->SetBoolean("did_submit_in_last_frame", did_submit_in_last_frame_);
+  state->SetBoolean("needs_impl_side_invalidation",
+                    needs_impl_side_invalidation_);
+  state->SetBoolean("impl_side_invalidations_take_priority",
+                    impl_side_invalidations_take_priority_);
   state->EndDictionary();
 }
 
@@ -558,6 +569,8 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
     return ACTION_PREPARE_TILES;
   if (ShouldSendBeginMainFrame())
     return ACTION_SEND_BEGIN_MAIN_FRAME;
+  if (ShouldPerformImplSideInvalidation())
+    return ACTION_PERFORM_IMPL_SIDE_INVALIDATION;
   if (ShouldInvalidateCompositorFrameSink())
     return ACTION_INVALIDATE_COMPOSITOR_FRAME_SINK;
   if (ShouldBeginCompositorFrameSinkCreation())
@@ -565,6 +578,90 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   return ACTION_NONE;
 }
 
+bool SchedulerStateMachine::ShouldPerformImplSideInvalidation() 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 wait on the response to BeginMainFrame if we are prioritizing impl
+  // side invalidations.
+  if (impl_side_invalidations_take_priority_)
+    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?
+  // See crbug.com/691735.
+  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)

[brianderson, 2017/02/21 23:34:59]

Given the preceding logic, I think the STATE_IDLE check can become a DCHECK.
Probably put the DCHECK within the if to maintain the relationship even though
it'll be true before the if.

[Khushal, 2017/02/22 20:24:02]

This code went away in the new patch, now that we just do it inside the
deadline, so the main frame state can be ignored.

+    return false;
+
+  // At this point, create a pending tree to run impl-side invalidations.
+  return true;
+}
+
+void SchedulerStateMachine::WillPerformImplSideInvalidation() {
+  WillPerformImplSideInvalidationInternal();
+}
+
+void SchedulerStateMachine::WillPerformImplSideInvalidationInternal() {
+  DCHECK(needs_impl_side_invalidation_);
+  DCHECK(!has_pending_tree_);
+
+  needs_impl_side_invalidation_ = false;
+  has_pending_tree_ = true;

[sunnyps, 2017/02/20 23:19:22]

For UI, has_pending_tree_ = true should never be true except between
SetNeedsCommit and ScheduledActionCommit.

[Khushal, 2017/02/21 09:43:44]

Good point. The impl-side invalidation should be done similar to a commit in
SingleThreadProxy. In ScheduledActionPerformImplSideInvalidation, right after we
invalidate the sync tree, it should immediately call NotifyReadyToActivate to
update the scheduler state correctly.

+  impl_side_invalidations_take_priority_ = 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;
+
+  // Don't create a pending tree till a frame sink is initialized.
+  if (!HasInitializedCompositorFrameSink())
+    return false;
+
+  return true;
+}
+
 void SchedulerStateMachine::WillSendBeginMainFrame() {
   DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
   DCHECK(visible_);
@@ -585,10 +682,24 @@ void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 
   if (!commit_has_no_updates) {
+    // If there was a commit, the impl-side invalidations will be merged with
+    // it. We always fill the impl-side invalidation funnel here, even if no
+    // request was currently pending, to defer creating another pending tree and
+    // performing PrepareTiles until the next frame, in case the invalidation
+    // request is received after the commit.
+    if (needs_impl_side_invalidation_)
+      WillPerformImplSideInvalidationInternal();
+    impl_side_invalidation_funnel_ = true;
+
     // Pending tree only exists if commit had updates.
     has_pending_tree_ = true;
     pending_tree_is_ready_for_activation_ = false;
     wait_for_ready_to_draw_ = settings_.commit_to_active_tree;
+  } else if (needs_impl_side_invalidation_) {
+    // If the main frame is getting aborted, the impl-side updates will end up
+    // continuously waiting on a commit. In this case, prioritize these over
+    // the main frame.
+    impl_side_invalidations_take_priority_ = true;
   }
 
   // Update state related to forced draws.
@@ -689,6 +800,10 @@ 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 +882,8 @@ 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 +943,7 @@ 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)