Revert "Moves the top_ and end_ words of the Scavenger into mutator thread."

runtime/vm/heap.h

Index: runtime/vm/heap.h
diff --git a/runtime/vm/heap.h b/runtime/vm/heap.h
index fc5e1748041b8a71e55f87303b64c82d7efc0be6..6c68d0fcba67c33c15698241232685e729f7627c 100644
--- a/runtime/vm/heap.h
+++ b/runtime/vm/heap.h
@@ -135,6 +135,10 @@ class Heap {
     old_space_.WriteProtectCode(read_only);
   }
 
+  // Accessors for inlined allocation in generated code.
+  static intptr_t TopOffset(Space space);
+  static intptr_t EndOffset(Space space);
+
   // Initialize the heap and register it with the isolate.
   static void Init(Isolate* isolate,
                    intptr_t max_new_gen_words,
@@ -339,7 +343,7 @@ class Heap {
   Isolate* isolate_;
 
   // The different spaces used for allocation.
-  Scavenger new_space_;
+  ALIGN8 Scavenger new_space_;
   PageSpace old_space_;
 
   WeakTable* new_weak_tables_[kNumWeakSelectors];