Create InternalHeap.

This is a heap wrapper that takes any HeapInterface and a MemoryNotificationInterface, and makes the heap notify all allocations as being for internal use.

BUG=
R=sebmarchand@chromium.org

Review URL: https://codereview.appspot.com/136890043

git-svn-id: http://sawbuck.googlecode.com/svn/trunk@2278 15e8cca8-e42c-11de-a347-f34a4f72eb7d