mac 10.7 SDK: Add missing protocols.

base/mac/cocoa_protocols.h

Index: base/mac/cocoa_protocols.h
diff --git a/base/mac/cocoa_protocols.h b/base/mac/cocoa_protocols.h
index 3e1d1e7617fe635a681c05f349138fcc91673973..314e7fa73cb5ee1fdfb89c4cd497b4472ce1d3e0 100644
--- a/base/mac/cocoa_protocols.h
+++ b/base/mac/cocoa_protocols.h
@@ -11,8 +11,8 @@
 // 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
@@ -22,6 +22,13 @@
 @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