views_examples: add Button sticker sheet

ui/views/examples/button_sticker_sheet.h

Index: ui/views/examples/button_sticker_sheet.h
diff --git a/ui/views/examples/button_sticker_sheet.h b/ui/views/examples/button_sticker_sheet.h
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+++ b/ui/views/examples/button_sticker_sheet.h
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+// 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 UI_VIEWS_EXAMPLES_BUTTON_STICKER_SHEET_H_
+#define UI_VIEWS_EXAMPLES_BUTTON_STICKER_SHEET_H_
+
+#include "base/macros.h"
+#include "ui/views/controls/button/button.h"
+#include "ui/views/examples/example_base.h"
+
+namespace views {
+namespace examples {
+
+// An "example" that displays a sticker sheet of all the available material
+// design button styles. This example only looks right with `--secondary-ui-md`.
+// It is designed to be as visually similar to the UI Harmony spec's sticker
+// sheet for buttons as possible.
+class VIEWS_EXAMPLES_EXPORT ButtonStickerSheet : public ExampleBase,
+                                                 public ButtonListener {
+ public:
+  ButtonStickerSheet();
+  ~ButtonStickerSheet() override;
+
+  // ExampleBase:
+  void CreateExampleView(View* container) override;
+
+  // ButtonListener:
+  void ButtonPressed(Button* sender, const ui::Event& event) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ButtonStickerSheet);
+};
+
+}  // namespace examples
+}  // namespace views
+
+#endif  // UI_VIEWS_EXAMPLES_BUTTON_STICKER_SHEET_H_