(not for commit) Simplified multi-threaded Ganesh with lock on Flush only.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 36c63c4fe2f181ffcb5d6005540650b300bd3bbd..6b9b69747cdaa8c87f9270a4a651a2eaee3b18c1 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -1129,11 +1129,13 @@ float PictureLayerImpl::MaximumTilingContentsScale() const {
 scoped_ptr<PictureLayerTilingSet>
 PictureLayerImpl::CreatePictureLayerTilingSet() {
   const LayerTreeSettings& settings = layer_tree_impl()->settings();
+  float skewport_scaling = 1.0f;
+  if (layer_tree_impl()->use_gpu_rasterization())
+    skewport_scaling =
+        settings.threaded_gpu_rasterization_enabled ? 0.2f : 0.0f;
   return PictureLayerTilingSet::Create(
       this, settings.max_tiles_for_interest_area,
-      layer_tree_impl()->use_gpu_rasterization()
-          ? 0.f
-          : settings.skewport_target_time_in_seconds,
+      settings.skewport_target_time_in_seconds * skewport_scaling,
       settings.skewport_extrapolation_limit_in_content_pixels);
 }