Mac: Some clang appeasing.

chrome/browser/cocoa/bookmark_button.h

Index: chrome/browser/cocoa/bookmark_button.h
diff --git a/chrome/browser/cocoa/bookmark_button.h b/chrome/browser/cocoa/bookmark_button.h
index 60dd2a6a335c21d33cac6831114b33d5209a4517..345980915b533e9cf03b3fdb8c36a9f8f50f1f0d 100644
--- a/chrome/browser/cocoa/bookmark_button.h
+++ b/chrome/browser/cocoa/bookmark_button.h
@@ -215,14 +215,14 @@ class ThemeProvider;
 namespace bookmark_button {
 
 // Notifications for pulsing of bookmarks.
-extern const NSString* kPulseBookmarkButtonNotification;
+extern NSString* const kPulseBookmarkButtonNotification;
 
 // Key for userInfo dict of a kPulseBookmarkButtonNotification.
 // Value is a [NSValue valueWithPointer:]; pointer is a (const BookmarkNode*).
-extern const NSString* kBookmarkKey;
+extern NSString* const kBookmarkKey;
 
 // Key for userInfo dict of a kPulseBookmarkButtonNotification.
 // Value is a [NSNumber numberWithBool:] to turn pulsing on or off.
-extern const NSString* kBookmarkPulseFlagKey;
+extern NSString* const kBookmarkPulseFlagKey;
 
 };