mac 10.7 SDK: Add missing protocols.

base/mac/cocoa_protocols.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 BASE_COCOA_PROTOCOLS_MAC_H_
 #define BASE_COCOA_PROTOCOLS_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 // GTM also maintinas a list of empty protocols, but only the ones the library
 // requires. Augment that below.
 #import "third_party/GTM/GTMDefines.h"
 
-// The Mac OS X 10.8 SDK introduced new protocols used for delegates.  These
-// protocol defintions were not present in earlier releases of the Mac OS X
+// New Mac OS X SDKs introduce new protocols used for delegates.  These
+// protocol defintions aren't not present in earlier releases of the Mac OS X
 // SDK.  In order to support building against the new SDK, which requires
 // delegates to conform to these protocols, and earlier SDKs, which do not
 // define these protocols at all, this file will provide empty protocol
 // definitions when used with earlier SDK versions.
 
 #define DEFINE_EMPTY_PROTOCOL(p) \
 @protocol p \
 @end
 
+#if !defined(MAC_OS_X_VERSION_10_7) || \
+    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
+
+DEFINE_EMPTY_PROTOCOL(NSDraggingDestination)
+
+#endif  // MAC_OS_X_VERSION_10_7
+
 #if !defined(MAC_OS_X_VERSION_10_8) || \
     MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_8
 
 DEFINE_EMPTY_PROTOCOL(NSUserNotificationCenterDelegate)
 
 #endif  // MAC_OS_X_VERSION_10_8
 
 #undef DEFINE_EMPTY_PROTOCOL
 
 #endif  // BASE_COCOA_PROTOCOLS_MAC_H_