cc: Adding BeginFrameTracker object and removing Now() from LTHI.

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index d8851e9665aa84141fa487d54b83dfda89a920af..b6335c2c51abc38e94f6dee469184712d98e4a94 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -179,6 +179,9 @@ class LayerTreeHostImplTest : public testing::Test,
         task_graph_runner_.get(), 0);
     bool init = host_impl_->InitializeRenderer(output_surface.Pass());
     host_impl_->SetViewportSize(gfx::Size(10, 10));
+    // Set the BeginFrameArgs so that methods which use it are able to.
+    host_impl_->WillBeginImplFrame(
+        CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE));
     return init;
   }
 
@@ -5049,6 +5052,8 @@ TEST_F(LayerTreeHostImplTest, PartialSwapReceivesDamageRect) {
           settings, this, &proxy_, &stats_instrumentation_,
           shared_bitmap_manager_.get(), NULL, task_graph_runner_.get(), 0);
   layer_tree_host_impl->InitializeRenderer(output_surface.Pass());
+  layer_tree_host_impl->WillBeginImplFrame(
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE));
   layer_tree_host_impl->SetViewportSize(gfx::Size(500, 500));
 
   scoped_ptr<LayerImpl> root =
@@ -5337,6 +5342,8 @@ static scoped_ptr<LayerTreeHostImpl> SetupLayersForOpacity(
   scoped_ptr<LayerTreeHostImpl> my_host_impl = LayerTreeHostImpl::Create(
       settings, client, proxy, stats_instrumentation, manager, NULL, NULL, 0);
   my_host_impl->InitializeRenderer(output_surface.Pass());
+  my_host_impl->WillBeginImplFrame(
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE));
   my_host_impl->SetViewportSize(gfx::Size(100, 100));
 
   /*