cc: Update scroll offset before property tree scrolling and animation.

cc/trees/layer_tree_host_in_process.cc

Index: cc/trees/layer_tree_host_in_process.cc
diff --git a/cc/trees/layer_tree_host_in_process.cc b/cc/trees/layer_tree_host_in_process.cc
index 57e2ea414e8bda672595b1955847274a3fc862d6..f4cd7c488f793a398d2615f6ef25361f0c6b124e 100644
--- a/cc/trees/layer_tree_host_in_process.cc
+++ b/cc/trees/layer_tree_host_in_process.cc
@@ -421,12 +421,13 @@ void LayerTreeHostInProcess::RequestMainFrameUpdate() {
 // this function, keep in mind that the function *runs* on the impl thread! Any
 // code that is logically a main thread operation, e.g. deletion of a Layer,
 // should be delayed until the LayerTreeHostInProcess::CommitComplete, which
-// will run
-// after the commit, but on the main thread.
+// will run after the commit, but on the main thread.
 void LayerTreeHostInProcess::FinishCommitOnImplThread(
     LayerTreeHostImpl* host_impl) {
   DCHECK(!IsRemoteServer());
-  DCHECK(task_runner_provider_->IsImplThread());
+  // The function may also be called by single threaded unit test.
+  DCHECK(task_runner_provider_->IsImplThread() ||
+         !task_runner_provider_->ImplThreadTaskRunner());

[ajuma, 2016/10/07 18:38:30]

Instead of calling this directly from your test, can you use a LayerTreeTest
(e.g. LayerTreeHostUnitTest or LayerTreeHostScrollTest) where this gets called
in the usual way?

 
   bool is_new_trace;
   TRACE_EVENT_IS_NEW_TRACE(&is_new_trace);
@@ -478,6 +479,10 @@ void LayerTreeHostInProcess::FinishCommitOnImplThread(
 
     TreeSynchronizer::PushLayerProperties(layer_tree_.get(), sync_tree);
 
+    // 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());
+
     // 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
@@ -491,10 +496,6 @@ void LayerTreeHostInProcess::FinishCommitOnImplThread(
         host_impl->animation_host());
   }
 
-  // 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());
-
   micro_benchmark_controller_.ScheduleImplBenchmarks(host_impl);
   layer_tree_->property_trees()->ResetAllChangeTracking();
 }