Make RootScroller set the outer viewport scroll layer in the compositor

cc/trees/root_scroller_controller.h

Index: cc/trees/root_scroller_controller.h
diff --git a/cc/trees/root_scroller_controller.h b/cc/trees/root_scroller_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..cfbc895b99720af7336e9d16ff0a0a15aa32eed6
--- /dev/null
+++ b/cc/trees/root_scroller_controller.h
@@ -0,0 +1,35 @@
+// Copyright 2016 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_TREES_ROOT_SCROLLER_CONTROLLER_H_
+#define CC_TREES_ROOT_SCROLLER_CONTROLLER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "cc/base/cc_export.h"
+
+namespace cc {
+
+class LayerImpl;
+class LayerTreeHostImpl;
+
+class CC_EXPORT RootScrollerController {
+ public:
+  static std::unique_ptr<RootScrollerController> Create();
+
+  void SetRootScrollerLayer(LayerImpl* layer);
+  LayerImpl* GetRootScrollerLayer();
+
+ private:
+  RootScrollerController();
+
+  LayerImpl* root_scroller_layer_;

[aelias_OOO_until_Jul13, 2016/06/29 22:44:08]

Please change this to an id, that avoids so many lifetime management headaches
and we really should not be persistently storing raw LayerImpl pointers
anywhere.

[bokan, 2016/07/07 21:20:45]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(RootScrollerController);
+};
+
+}  // namespace cc
+
+#endif  // CC_TREES_ROOT_SCROLLER_CONTROLLER_H_