Fix typo in Add|RemoveGCPrologueCallback

BUG=

Review URL: https://chromiumcodereview.appspot.com/10836234
Patch from Yang Gu <yang.gu@intel.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12339 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.h

@@ -1102,8 +1102,8 @@ class Heap {
 #endif
 
   void AddGCPrologueCallback(
-      GCEpilogueCallback callback, GCType gc_type_filter);
-  void RemoveGCPrologueCallback(GCEpilogueCallback callback);
+      GCPrologueCallback callback, GCType gc_type_filter);
+  void RemoveGCPrologueCallback(GCPrologueCallback callback);
 
   void AddGCEpilogueCallback(
       GCEpilogueCallback callback, GCType gc_type_filter);