[Isolates] Clean up some usages of the heap macro.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index c358b76d8425ff90d60e2845578d0a25590f1581..a679339bc088261eb8850cbfa0c33dd800faeac4 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -1562,7 +1562,8 @@ static void UpdatePointerToNewGen(HeapObject** p) {
 }
 
 
-static String* UpdateNewSpaceReferenceInExternalStringTableEntry(Object **p) {
+static String* UpdateNewSpaceReferenceInExternalStringTableEntry(Heap* heap,
+                                                                 Object** p) {
   Address old_addr = HeapObject::cast(*p)->address();
   Address new_addr = Memory::Address_at(old_addr);
   return String::cast(HeapObject::FromAddress(new_addr));