[cc] Move root layer pointer to LayerTreeImpl

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..52928f1bd530b08fe395206367390190ad957c1c
--- /dev/null
+++ b/cc/layer_tree_impl.h
@@ -0,0 +1,66 @@
+// Copyright 2012 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.
+
+#ifndef CC_LAYER_TREE_IMPL_H_
+#define CC_LAYER_TREE_IMPL_H_
+
+#include "cc/layer_impl.h"
+
+namespace cc {
+
+class LayerTreeHostImpl;
+class LayerTreeImpl;
+class HeadsUpDisplayLayerImpl;
+
+class CC_EXPORT LayerTreeImplClient {
+ public:
+  virtual void OnCanDrawStateChangedForTree(LayerTreeImpl*)  = 0;
+
+ protected:
+  virtual ~LayerTreeImplClient() {}
+};
+
+class CC_EXPORT LayerTreeImpl {
+ public:
+  static scoped_ptr<LayerTreeImpl> create(LayerTreeImplClient* client)
+  {
+    return make_scoped_ptr(new LayerTreeImpl(client));
+  }
+  virtual ~LayerTreeImpl();
+
+  LayerImpl* RootLayer() const { return root_layer_.get(); }
+  void SetRootLayer(scoped_ptr<LayerImpl>);
+  scoped_ptr<LayerImpl> DetachLayerTree();
+
+  int source_frame_number() const { return source_frame_number_; }
+  void set_source_frame_number(int frame_number) { source_frame_number_ = frame_number; }
+
+  HeadsUpDisplayLayerImpl* hud_layer() { return hud_layer_; }
+  void set_hud_layer(HeadsUpDisplayLayerImpl* layer_impl) { hud_layer_ = layer_impl; }
+
+  LayerImpl* root_scroll_layer() { return root_scroll_layer_; }
+  void set_root_scroll_layer(LayerImpl* layer_impl) { root_scroll_layer_ = layer_impl; }
+
+  LayerImpl* currently_scrolling_layer() { return currently_scrolling_layer_; }
+  void set_currently_scrolling_layer(LayerImpl* layer_impl) { currently_scrolling_layer_ = layer_impl; }
+
+protected:
+  LayerTreeImpl(LayerTreeImplClient* client);
+
+  LayerTreeImplClient* client_;
+  int source_frame_number_;
+  scoped_ptr<LayerImpl> root_layer_;
+  HeadsUpDisplayLayerImpl* hud_layer_;
+  LayerImpl* root_scroll_layer_;
+  LayerImpl* currently_scrolling_layer_;
+
+  // Persisted state
+  int scrolling_layer_id_from_previous_tree_;
+
+  DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
+};
+
+}
+
+#endif  // CC_LAYER_TREE_IMPL_H_