Harmonize LayerTreeHost/LayerTreeHostImpl synchronization steps

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 62e587ce860fceb390dcb40e31992f43b843aa36..7da2e05c62d0b5750ef825c4d0f50b64479041a6 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -243,6 +243,9 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       has_scrolled_by_wheel_(false),
       has_scrolled_by_touch_(false),
       touchpad_and_wheel_scroll_latching_enabled_(false),
+#if DCHECK_IS_ON()
+      sync_state_(NOT_SYNCING),
+#endif
       impl_thread_phase_(ImplThreadPhase::IDLE) {
   DCHECK(mutator_host_);
   mutator_host_->SetMutatorHostClient(this);
@@ -2046,6 +2049,8 @@ void LayerTreeHostImpl::CreatePendingTree() {
 
 void LayerTreeHostImpl::ActivateSyncTree() {
   if (pending_tree_) {
+    DCHECK(AdvanceSyncState(BEGINNING_SYNC));
+
     TRACE_EVENT_ASYNC_END0("cc", "PendingTree:waiting", pending_tree_.get());
 
     DCHECK(pending_tree_duration_timer_);
@@ -2073,14 +2078,23 @@ void LayerTreeHostImpl::ActivateSyncTree() {
       else
         active_tree_->MoveChangeTrackingToLayers();
     }
-    TreeSynchronizer::PushLayerProperties(pending_tree(), active_tree());
+
     active_tree_->property_trees()->PushOpacityIfNeeded(
         pending_tree_->property_trees());
+    pending_tree_->PushPropertyTreesTo(active_tree_.get());
+    DCHECK(AdvanceSyncState(SYNCED_PROPERTY_TREES));
+
+    TreeSynchronizer::PushLayerProperties(pending_tree(), active_tree());
+    DCHECK(AdvanceSyncState(SYNCED_LAYER_PROPERTIES));
 
     pending_tree_->PushPropertiesTo(active_tree_.get());
+    DCHECK(AdvanceSyncState(SYNCED_LAYER_TREE_HOST_PROPERTIES));
+
     if (!pending_tree_->LayerListIsEmpty())
       pending_tree_->property_trees()->ResetAllChangeTracking();
 
+    DCHECK(AdvanceSyncState(NOT_SYNCING));
+
     // Now that we've synced everything from the pending tree to the active
     // tree, rename the pending tree the recycle tree so we can reuse it on the
     // next sync.