Update from https://crrev.com/316786

cc/trees/single_thread_proxy.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/debug/benchmark_instrumentation.h"
 #include "cc/debug/devtools_instrumentation.h"
@@ skipping 64 matching lines @@
     DebugScopedSetImplThread impl(this);
     layer_tree_host_impl_->FinishAllRendering();
   }
 }
 
 bool SingleThreadProxy::IsStarted() const {
   DCHECK(Proxy::IsMainThread());
   return layer_tree_host_impl_;
 }
 
+bool SingleThreadProxy::CommitToActiveTree() const {
+  // With SingleThreadProxy we skip the pending tree and commit directly to the
+  // active tree.
+  return true;
+}
+
 void SingleThreadProxy::SetLayerTreeHostClientReady() {
   TRACE_EVENT0("cc", "SingleThreadProxy::SetLayerTreeHostClientReady");
   // Scheduling is controlled by the embedder in the single thread case, so
   // nothing to do.
   DCHECK(Proxy::IsMainThread());
   DebugScopedSetImplThread impl(this);
   if (layer_tree_host_->settings().single_thread_proxy_scheduler &&
       !scheduler_on_impl_thread_) {
     SchedulerSettings scheduler_settings(layer_tree_host_->settings());
     // SingleThreadProxy should run in main thread low latency mode.
@@ skipping 138 matching lines @@
             MainThreadTaskRunner(),
             queue_for_commit_.Pass(),
             layer_tree_host_impl_->resource_provider());
     update_controller->Finalize();
 
     if (layer_tree_host_impl_->EvictedUIResourcesExist())
       layer_tree_host_->RecreateUIResources();
 
     layer_tree_host_->FinishCommitOnImplThread(layer_tree_host_impl_.get());
 
-    layer_tree_host_impl_->CommitComplete();
-
 #if DCHECK_IS_ON()
     // In the single-threaded case, the scale and scroll deltas should never be
     // touched on the impl layer tree.
     scoped_ptr<ScrollAndScaleSet> scroll_info =
         layer_tree_host_impl_->ProcessScrollDeltas();
     DCHECK(!scroll_info->scrolls.size());
     DCHECK_EQ(1.f, scroll_info->page_scale_delta);
 #endif
-  }
 
-  if (layer_tree_host_->settings().impl_side_painting) {
-    // TODO(enne): just commit directly to the active tree.
-    //
-    // Synchronously activate during commit to satisfy any potential
-    // SetNextCommitWaitsForActivation calls.  Unfortunately, the tree
-    // might not be ready to draw, so DidActivateSyncTree must set
-    // the flag to force the tree to not draw until textures are ready.
-    NotifyReadyToActivate();
-  } else {
-    CommitComplete();
+    if (layer_tree_host_->settings().impl_side_painting) {
+      // Commit goes directly to the active tree, but we need to synchronously
+      // "activate" the tree still during commit to satisfy any potential
+      // SetNextCommitWaitsForActivation calls.  Unfortunately, the tree
+      // might not be ready to draw, so DidActivateSyncTree must set
+      // the flag to force the tree to not draw until textures are ready.
+      NotifyReadyToActivate();
+    } else {
+      CommitComplete();
+    }
   }
 }
 
 void SingleThreadProxy::CommitComplete() {
   DCHECK(!layer_tree_host_impl_->pending_tree())
       << "Activation is expected to have synchronously occurred by now.";
   DCHECK(commit_blocking_task_runner_);
 
+  // Notify commit complete on the impl side after activate to satisfy any
+  // SetNextCommitWaitsForActivation calls.
+  layer_tree_host_impl_->CommitComplete();
+
   DebugScopedSetMainThread main(this);
   commit_blocking_task_runner_.reset();
   layer_tree_host_->CommitComplete();
   layer_tree_host_->DidBeginMainFrame();
   timing_history_.DidCommit();
 
   next_frame_is_newly_committed_frame_ = true;
 }
 
 void SingleThreadProxy::SetNeedsCommit() {
@@ skipping 143 matching lines @@
   return contents_texture_manager->ReduceMemoryOnImplThread(
       limit_bytes, priority_cutoff, resource_provider);
 }
 
 bool SingleThreadProxy::IsInsideDraw() { return inside_draw_; }
 
 void SingleThreadProxy::DidActivateSyncTree() {
   // Non-impl-side painting finishes commit in DoCommit.  Impl-side painting
   // defers until here to simulate SetNextCommitWaitsForActivation.
   if (layer_tree_host_impl_->settings().impl_side_painting) {
-    // This is required because NotifyReadyToActivate gets called when
-    // the pending tree is not actually ready in the SingleThreadProxy.
+    // This is required because NotifyReadyToActivate gets called immediately
+    // after commit since single thread commits directly to the active tree.
     layer_tree_host_impl_->SetRequiresHighResToDraw();
 
     // Synchronously call to CommitComplete. Resetting
     // |commit_blocking_task_runner| would make sure all tasks posted during
     // commit/activation before CommitComplete.
     CommitComplete();
   }
 
   timing_history_.DidActivateSyncTree();
 }
@@ skipping 87 matching lines @@
     LayerTreeHostImpl::FrameData frame;
     DoComposite(frame_begin_time, &frame);
 
     // DoComposite could abort, but because this is a synchronous composite
     // another draw will never be scheduled, so break remaining promises.
     layer_tree_host_impl_->active_tree()->BreakSwapPromises(
         SwapPromise::SWAP_FAILS);
   }
 }
 
-void SingleThreadProxy::AsValueInto(base::debug::TracedValue* state) const {
+void SingleThreadProxy::AsValueInto(
+    base::trace_event::TracedValue* state) const {
   // The following line casts away const modifiers because it is just
   // setting debug state. We still want the AsValue() function and its
   // call chain to be const throughout.
   DebugScopedSetImplThread impl(const_cast<SingleThreadProxy*>(this));
 
   state->BeginDictionary("layer_tree_host_impl");
   layer_tree_host_impl_->AsValueInto(state);
   state->EndDictionary();
 }
 
@@ skipping 262 matching lines @@
 
 void SingleThreadProxy::DidBeginImplFrameDeadline() {
   layer_tree_host_impl_->ResetCurrentBeginFrameArgsForNextFrame();
 }
 
 void SingleThreadProxy::SendBeginFramesToChildren(const BeginFrameArgs& args) {
   layer_tree_host_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc