Update from chromium https://crrev.com/302282

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/debug/trace_event.h"
 #include "cc/debug/benchmark_instrumentation.h"
 #include "cc/output/context_provider.h"
@@ skipping 449 matching lines @@
 void SingleThreadProxy::DidSwapBuffersCompleteOnImplThread() {
   TRACE_EVENT0("cc", "SingleThreadProxy::DidSwapBuffersCompleteOnImplThread");
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->DidSwapBuffersComplete();
   layer_tree_host_->DidCompleteSwapBuffers();
 }
 
 void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
   TRACE_EVENT0("cc", "SingleThreadProxy::CompositeImmediately");
   DCHECK(Proxy::IsMainThread());
-  DCHECK(!layer_tree_host_impl_->settings().impl_side_painting)
-      << "Impl-side painting and synchronous compositing are not supported.";
   base::AutoReset<bool> inside_composite(&inside_synchronous_composite_, true);
 
   if (layer_tree_host_->output_surface_lost()) {
     RequestNewOutputSurface();
     // RequestNewOutputSurface could have synchronously created an output
     // surface, so check again before returning.
     if (layer_tree_host_->output_surface_lost())
       return;
   }
 
   {
     BeginFrameArgs begin_frame_args(
         BeginFrameArgs::Create(frame_begin_time,
                                base::TimeTicks(),
                                BeginFrameArgs::DefaultInterval()));
     DoBeginMainFrame(begin_frame_args);
     DoCommit();
 
     DCHECK_EQ(0u, layer_tree_host_->num_queued_swap_promises())
         << "Commit should always succeed and transfer promises.";
   }
 
   {
     DebugScopedSetImplThread impl(const_cast<SingleThreadProxy*>(this));
+    if (layer_tree_host_impl_->settings().impl_side_painting) {
+      layer_tree_host_impl_->ActivateSyncTree();
+      layer_tree_host_impl_->active_tree()->UpdateDrawProperties();
+      layer_tree_host_impl_->ManageTiles();
+      layer_tree_host_impl_->SynchronouslyInitializeAllTiles();
+    }
+
     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);
   }
 }
 
@@ skipping 279 matching lines @@
 
 base::TimeDelta SingleThreadProxy::CommitToActivateDurationEstimate() {
   return timing_history_.CommitToActivateDurationEstimate();
 }
 
 void SingleThreadProxy::DidBeginImplFrameDeadline() {
   layer_tree_host_impl_->ResetCurrentBeginFrameArgsForNextFrame();
 }
 
 }  // namespace cc