cc: Send all begin frames using a PostTask.

services/ui/surfaces/display_compositor.cc

Index: services/ui/surfaces/display_compositor.cc
diff --git a/services/ui/surfaces/display_compositor.cc b/services/ui/surfaces/display_compositor.cc
index bdf1424b35ab543bc6ca24382011e47ad98a681a..19305c86bee346fbb2ab624034195783a8a4b339 100644
--- a/services/ui/surfaces/display_compositor.cc
+++ b/services/ui/surfaces/display_compositor.cc
@@ -41,8 +41,7 @@ DisplayCompositor::DisplayCompositor(
   CHECK(surfaces_context_provider->BindToCurrentThread());
 
   std::unique_ptr<cc::SyntheticBeginFrameSource> synthetic_begin_frame_source(
-      new cc::DelayBasedBeginFrameSource(
-          base::MakeUnique<cc::DelayBasedTimeSource>(task_runner_.get())));
+      new cc::DelayBasedBeginFrameSource(task_runner_.get()));
 
   std::unique_ptr<cc::OutputSurface> display_output_surface;
   if (surfaces_context_provider->ContextCapabilities().surfaceless) {