WIP - compositor worker mega patch.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 203670f6be57d8cc0298194af7410bda4f468cc3..2e21bed1f621a802e4370332c8f2e5b702eff8db 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -224,7 +224,9 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       shared_bitmap_manager_(shared_bitmap_manager),
       gpu_memory_buffer_manager_(gpu_memory_buffer_manager),
       task_graph_runner_(task_graph_runner),
+      mutator_(nullptr),
       id_(id),
+      is_scrolling_(false),
       requires_high_res_to_draw_(false),
       is_likely_to_require_a_draw_(false),
       frame_timing_tracker_(FrameTimingTracker::Create(this)) {
@@ -326,7 +328,7 @@ void LayerTreeHostImpl::BeginCommit() {
 }
 
 void LayerTreeHostImpl::CommitComplete() {
-  TRACE_EVENT0("cc", "LayerTreeHostImpl::CommitComplete");
+  TRACE_EVENT0("cc,compositor-worker", "LayerTreeHostImpl::CommitComplete");
 
   if (CommitToActiveTree()) {
     // We have to activate animations here or "IsActive()" is true on the layers
@@ -457,6 +459,8 @@ void LayerTreeHostImpl::AnimateInternal(bool active_tree) {
   did_animate |= AnimateTopControls(monotonic_time);
 
   if (active_tree) {
+    did_animate |= Mutate(monotonic_time);
+
     // Animating stuff can change the root scroll offset, so inform the
     // synchronous input handler.
     UpdateRootLayerStateForSynchronousInputHandler();
@@ -468,6 +472,20 @@ void LayerTreeHostImpl::AnimateInternal(bool active_tree) {
   }
 }
 
+bool LayerTreeHostImpl::Mutate(base::TimeTicks monotonic_time) {
+  if (!mutator_)
+    return false;
+  TRACE_EVENT0("compositor-worker", "LayerTreeHostImpl::Mutate");
+  if (mutator_->Mutate(monotonic_time, active_tree_.get()))
+    client_->SetNeedsOneBeginImplFrameOnImplThread();
+  return true;
+}
+
+void LayerTreeHostImpl::SetNeedsMutate() {
+  TRACE_EVENT0("compositor-worker", "LayerTreeHostImpl::SetNeedsMutate");
+  client_->SetNeedsOneBeginImplFrameOnImplThread();
+}
+
 bool LayerTreeHostImpl::PrepareTiles() {
   if (!tile_priorities_dirty_)
     return false;
@@ -2038,6 +2056,7 @@ void LayerTreeHostImpl::ActivateSyncTree() {
     // If we commit to the active tree directly, this is already done during
     // commit.
     ActivateAnimations();
+    Mutate(CurrentBeginFrameArgs().frame_time);
   } else {
     active_tree_->ProcessUIResourceRequestQueue();
   }
@@ -2287,6 +2306,14 @@ void LayerTreeHostImpl::PostFrameTimingEvents(
                                              std::move(main_frame_events));
 }
 
+void LayerTreeHostImpl::SetLayerTreeMutator(LayerTreeMutator* mutator) {
+  if (mutator == mutator_)
+    return;
+  TRACE_EVENT0("compositor-worker", "LayerTreeHostImpl::SetLayerTreeMutator");
+  mutator_ = mutator;
+  mutator_->SetClient(this);
+}
+
 void LayerTreeHostImpl::CleanUpTileManagerAndUIResources() {
   ClearUIResources();
   tile_manager_->FinishTasksAndCleanUp();
@@ -2737,6 +2764,7 @@ gfx::Vector2dF LayerTreeHostImpl::ScrollLayer(LayerImpl* layer_impl,
   // screen (such as wheel events) represent a fixed amount of scrolling so we
   // can just apply them directly, but the page scale factor is applied to the
   // scroll delta.
+  base::AutoReset<bool> reset(&is_scrolling_, true);
   if (is_direct_manipulation) {
     return ScrollLayerWithViewportSpaceDelta(
         layer_impl, gfx::PointF(viewport_point), delta);
@@ -2803,6 +2831,7 @@ InputHandlerScrollResult LayerTreeHostImpl::ScrollBy(
     const gfx::Point& viewport_point,
     const gfx::Vector2dF& scroll_delta) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::ScrollBy");
+  base::AutoReset<bool> reset(&is_scrolling_, true);
   if (!CurrentlyScrollingLayer())
     return InputHandlerScrollResult();
 
@@ -2877,6 +2906,9 @@ InputHandlerScrollResult LayerTreeHostImpl::ScrollBy(
   // input handler.
   UpdateRootLayerStateForSynchronousInputHandler();
 
+  // Update compositor worker mutations which may respond to scrolling.
+  Mutate(CurrentBeginFrameArgs().frame_time);
+
   return scroll_result;
 }