Add generic PaletteDelegate code.

ash/common/palette_delegate.h

+// 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 ASH_COMMON_PALETTE_DELEGATE_H_
+#define ASH_COMMON_PALETTE_DELEGATE_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+
+namespace ash {
+
+// This delegate allows the UI code in ash, e.g. |PaletteTray|, to perform
+// Chrome-specific actions.
+class PaletteDelegate {
+ public:
+  virtual ~PaletteDelegate() {}
+

[Daniel Erat, 2016/08/05 15:48:52]

maybe add a "TODO(jdufault): Add methods: http://crbug.com/[whatever]" here so
people don't get confused about why this is empty? :-)

[jdufault, 2016/08/05 19:03:37]

Done.

+ private:
+  DISALLOW_ASSIGN(PaletteDelegate);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_PALETTE_DELEGATE_H_