Enlarge size of touch target for several location bar buttons without affecting visual layout.

chrome/browser/ui/views/location_bar/touchable_location_bar_view.h

+// Copyright (c) 2012 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_LOCATION_BAR_TOUCHABLE_LOCATION_BAR_VIEW_H_
+#define CHROME_BROWSER_UI_VIEWS_LOCATION_BAR_TOUCHABLE_LOCATION_BAR_VIEW_H_
+#pragma once
+
+#include "ui/views/view.h"
+
+// An interface for a View in within the LocationBar that knows how to
+// increase its size (without affecting visual layout) in a touch
+// layout, to increase the size of the touch target.  Its border
+// extends a few pixels up and down, which doesn't affect layout, and
+// extends half of the padding used between items in the location bar
+// to the left and right.
+//
+// To make your location bar View extend itself into the padding
+// around it to get an enlarged touch target, inherit from
+// TouchableLocationBarView interface, implement its
+// GetBuiltInHorizontalPadding method by calling
+// GetBuiltInHorizontalPaddingImpl, and call
+// TouchableLocationBarView::Init() from your constructor.
+class TouchableLocationBarView {
+ public:
+  // Returns the number of pixels of built-in padding to the left and
+  // right of the image for this view.
+  virtual int GetBuiltInHorizontalPadding() const = 0;
+
+ protected:
+  // Call this from the constructor (or during early initialization)
+  // of a class that inherits from TouchableLocationBarView.
+  static void Init(views::View* view);
+
+  // Use this to implement GetBuiltInHorizontalPadding().
+  static int GetBuiltInHorizontalPaddingImpl();
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_LOCATION_BAR_TOUCHABLE_LOCATION_BAR_VIEW_H_