Initial attempt at counting layers in the compositor thread.

cc/trees/layer_tree_impl_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/test/fake_impl_proxy.h"
 #include "cc/test/fake_layer_tree_host_impl.h"
@@ skipping 2301 matching lines @@
   EXPECT_EQ(left_input.layer_rect, left_output.viewport_rect);
   EXPECT_TRUE(left_output.visible);
   EXPECT_EQ(right_input.type, right_output.type);
   gfx::RectF expected_right_output_rect = right_input.layer_rect;
   expected_right_output_rect.Offset(sub_layer_offset);
   expected_right_output_rect.Scale(page_scale_factor);
   EXPECT_EQ(expected_right_output_rect, right_output.viewport_rect);
   EXPECT_TRUE(right_output.visible);
 }
 
+TEST_F(LayerTreeImplTest, NumLayersTestOne) {
+  EXPECT_EQ(0u, host_impl().active_tree()->NumLayers());
+  scoped_ptr<LayerImpl> root = LayerImpl::Create(host_impl().active_tree(), 1);
+  EXPECT_EQ(1u, host_impl().active_tree()->NumLayers());
+}
+
+TEST_F(LayerTreeImplTest, NumLayersSmallTree) {
+  EXPECT_EQ(0u, host_impl().active_tree()->NumLayers());
+  scoped_ptr<LayerImpl> root = LayerImpl::Create(host_impl().active_tree(), 1);
+  root->AddChild(LayerImpl::Create(host_impl().active_tree(), 2));
+  root->AddChild(LayerImpl::Create(host_impl().active_tree(), 3));
+  root->child_at(1)->AddChild(LayerImpl::Create(host_impl().active_tree(), 4));
+  EXPECT_EQ(4u, host_impl().active_tree()->NumLayers());
+}
+
 }  // namespace
 }  // namespace cc