Adds USB writing for OS X.

chrome/common/extensions/image_writer/image_writer_util_mac.h

Index: chrome/common/extensions/image_writer/image_writer_util_mac.h
diff --git a/chrome/common/extensions/image_writer/image_writer_util_mac.h b/chrome/common/extensions/image_writer/image_writer_util_mac.h
new file mode 100644
index 0000000000000000000000000000000000000000..a81f8d97b2f4580765635da335b989ee2e7843bd
--- /dev/null
+++ b/chrome/common/extensions/image_writer/image_writer_util_mac.h
@@ -0,0 +1,21 @@
+// Copyright 2014 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_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H_
+#define CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H_
+
+#include <CoreFoundation/CoreFoundation.h>
+
+namespace extensions {
+namespace image_writer {
+
+// Determines if the disk described by the dictionary is a removable USB or SD
+// drive.  The dictionary should be one as returned by |DADiskCopyDescription|.
+// The caller retains ownership of the dictionary.
+bool IsRemovableDevice(CFDictionaryRef disk_description);
+
+}  // image_writer
+}  // extensions
+
+#endif  // CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_H_