Reland "[heap] No leakage of mark-compact.h outside of heap."

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index b4b5c21a50bd7994a9e7bbdd417f9cb88ffd075d..c3dd5d3625ee46d57f5fb0d8608fdaa44c9233d8 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -14,8 +14,7 @@
 #include "src/assert-scope.h"
 #include "src/atomic-utils.h"
 #include "src/globals.h"
-// TODO(mstarzinger): Three more includes to kill!
-#include "src/heap/mark-compact.h"
+// TODO(mstarzinger): Two more includes to kill!
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
 #include "src/list.h"
@@ -1108,7 +1107,7 @@ class Heap {
   inline Isolate* isolate();
 
   MarkCompactCollector* mark_compact_collector() {
-    return &mark_compact_collector_;
+    return mark_compact_collector_;
   }
 
   // ===========================================================================
@@ -2279,7 +2278,7 @@ class Heap {
 
   Scavenger* scavenge_collector_;
 
-  MarkCompactCollector mark_compact_collector_;
+  MarkCompactCollector* mark_compact_collector_;
 
   StoreBuffer store_buffer_;