Mac: Update zoom bubble UI

ui/native_theme/native_theme_mac.h

Index: ui/native_theme/native_theme_mac.h
diff --git a/ui/native_theme/native_theme_mac.h b/ui/native_theme/native_theme_mac.h
new file mode 100644
index 0000000000000000000000000000000000000000..20378426db5bdac63a7d7a552e15310c852d1f77
--- /dev/null
+++ b/ui/native_theme/native_theme_mac.h
@@ -0,0 +1,28 @@
+// Copyright (c) 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 UI_NATIVE_THEME_NATIVE_THEME_MAC_H_
+#define UI_NATIVE_THEME_NATIVE_THEME_MAC_H_
+
+#include "ui/native_theme/native_theme_base.h"
+
+namespace ui {
+
+// Mac implementation of native theme support.
+class NativeThemeMac : public NativeThemeBase {
+ public:
+  static NativeThemeMac* instance();

[Scott Hess - ex-Googler, 2013/02/27 15:22:10]

This seems odd to expose.  Wouldn't it only be necessary if the native-theme
abstraction were broken?

[sail, 2013/02/27 18:48:18]

This is consistent with the other platforms. From what I understand this is used
to conditionally change the UI based on the theme used. Here's an example:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/...

[Scott Hess - ex-Googler, 2013/02/27 19:01:58]

Say no more, say no more.  Please, say no more, I think this is going somewhere
I don't want to know about!

+
+  virtual SkColor GetSystemColor(ColorId color_id) const OVERRIDE;
+
+ private:
+  NativeThemeMac();
+  virtual ~NativeThemeMac();
+
+  DISALLOW_COPY_AND_ASSIGN(NativeThemeMac);
+};
+
+}  // namespace ui
+
+#endif  // UI_NATIVE_THEME_NATIVE_THEME_MAC_H_