Fix header guards in //chrome

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
index 5b1c82c0b995d7b9b2f24d03b4759bcf9efce79a..99eebebc73f79c6ba52d3b8879738179ccf2b03d 100644
--- a/chrome/common/extensions/image_writer/image_writer_util_mac.h
+++ b/chrome/common/extensions/image_writer/image_writer_util_mac.h
@@ -2,8 +2,8 @@
 // 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
+#ifndef CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H_
+#define CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H_
 
 #include <IOKit/IOKitLib.h>
 
@@ -16,4 +16,4 @@ bool IsUsbDevice(io_object_t disk_obj);
 
 }  // namespace extensions
 
-#endif  // CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H
+#endif  // CHROME_COMMON_EXTENSIONS_IMAGE_WRITER_IMAGE_WRITER_UTIL_MAC_H_