Make HashMap a template class to specify the allocation policy.

src/compilation-cache.h

Index: src/compilation-cache.h
===================================================================
--- src/compilation-cache.h	(revision 10795)
+++ src/compilation-cache.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright 2011 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -31,8 +31,6 @@
 namespace v8 {
 namespace internal {
 
-class HashMap;
-
 // The compilation cache consists of several generational sub-caches which uses
 // this class as a base class. A sub-cache contains a compilation cache tables
 // for each generation of the sub-cache. Since the same source code string has