cc: Don't create SyncedPropety instances on the main thread.

cc/trees/layer_tree_host_in_process.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/layer_tree_host_in_process.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 341 matching lines @@
         PropertyTrees* property_trees = layer_tree_->property_trees();
         property_trees->scroll_tree.SetScrollOffset(
             layer_id, gfx::ScrollOffsetWithDelta(
                           layer_tree_->LayerById(layer_id)->scroll_offset(),
                           scroll_delta));
       }
     }
 
     // This must happen after synchronizing property trees and after pushing
     // properties, which updates the clobber_active_value flag.
-    sync_tree->UpdatePropertyTreeScrollOffset(layer_tree_->property_trees());
+    sync_tree->property_trees()->scroll_tree.PushScrollUpdatesFromMainThread(
+        layer_tree_->property_trees(), sync_tree);
 
     // This must happen after synchronizing property trees and after push
     // properties, which updates property tree indices, but before animation
     // host pushes properties as animation host push properties can change
     // Animation::InEffect and we want the old InEffect value for updating
     // property tree scrolling and animation.
     sync_tree->UpdatePropertyTreeScrollingAndAnimationFromMainThread();
 
     TRACE_EVENT0("cc", "LayerTreeHostInProcess::AnimationHost::PushProperties");
     DCHECK(host_impl->mutator_host());
@@ skipping 479 matching lines @@
   return compositor_mode_ == CompositorMode::SINGLE_THREADED;
 }
 
 bool LayerTreeHostInProcess::IsThreaded() const {
   DCHECK(compositor_mode_ != CompositorMode::THREADED ||
          task_runner_provider_->HasImplThread());
   return compositor_mode_ == CompositorMode::THREADED;
 }
 
 }  // namespace cc