[Toolbar] Base toolbar button class with background images for button states

chrome/browser/ui/views/toolbar/back_button.h

+// Copyright 2013 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 CHROME_BROWSER_UI_VIEWS_TOOLBAR_BACK_BUTTON_H_
+#define CHROME_BROWSER_UI_VIEWS_TOOLBAR_BACK_BUTTON_H_
+
+#include "chrome/browser/ui/views/toolbar/toolbar_button.h"
+
+namespace ui {
+class MenuModel;
+}
+
+namespace views {
+class ButtonListener;
+}
+
+// A subclass of ToolbarButton to allow the back button's hittest region to
+// extend all the way to the start of the toolbar (i.e. the screen edge) in
+// maximized mode, to benefit from Fitt's Law.  The button images and focus
+// border are still drawn with the normal square shape.
+class BackButton : public ToolbarButton {
+ public:
+  // Takes ownership of the |model|, which can be null if no menu
+  // is to be shown.
+  BackButton(views::ButtonListener* listener, ui::MenuModel* model);
+  virtual ~BackButton();
+
+  void SetLeadingMargin(int margin);
+
+ protected:
+  virtual gfx::Rect GetThemePaintRect() const OVERRIDE;
+
+ private:
+  // Any leading margin to be applied. Used when the back button is in
+  // a maximized state to extend to the full window width.
+  int margin_leading_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackButton);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_TOOLBAR_BACK_BUTTON_H_