Add common palette tray implementation.

ash/common/system/chromeos/palette/common_palette_tool.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_SYSTEM_CHROMEOS_PALETTE_COMMON_PALETTE_TOOL_H_
+#define ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_COMMON_PALETTE_TOOL_H_
+
+#include "ash/common/system/chromeos/palette/palette_tool.h"
+#include "ash/common/system/tray/hover_highlight_view.h"
+#include "ash/common/system/tray/view_click_listener.h"
+#include "base/strings/string16.h"
+#include "ui/gfx/vector_icons_public.h"
+
+namespace ash {
+
+// A PaletteTool implementation with a standard view support.
+class CommonPaletteTool : public PaletteTool, public ash::ViewClickListener {
+ protected:
+  explicit CommonPaletteTool(Delegate* delegate);
+  ~CommonPaletteTool() override;
+
+  // PaletteTool:
+  views::View* CreateView() override;
+  void OnViewDestroyed() override;
+  void OnEnable() override;
+  void OnDisable() override;
+
+  // ViewClickListener:
+  void OnViewClicked(views::View* sender) override;
+
+  // Returns the icon used in the palette tray on the left-most edge of the
+  // tool.
+  virtual gfx::VectorIconId GetPaletteIconId() = 0;
+
+  // Creates a default view implementation to be returned by CreateView.
+  views::View* CreateDefaultView(const base::string16& name);
+
+ private:
+  HoverHighlightView* highlight_view_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(CommonPaletteTool);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_COMMON_PALETTE_TOOL_H_