Cleanup of Isolate usage (guided by SunSpider profiling)

src/mark-compact.cc

 // Copyright 2006-2008 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 650 matching lines @@
   static inline bool IsJSBuiltinsObject(Object* obj) {
     return obj->IsHeapObject() &&
         (SafeMap(obj)->instance_type() == JS_BUILTINS_OBJECT_TYPE);
   }
 
 
   static inline bool IsValidNotBuiltinContext(Object* ctx) {
     if (!ctx->IsHeapObject()) return false;
 
     Map* map = SafeMap(ctx);
-    if (!(map == HEAP->raw_unchecked_context_map() ||
-          map == HEAP->raw_unchecked_catch_context_map() ||
-          map == HEAP->raw_unchecked_global_context_map())) {
+    Heap* heap = map->heap();
+    if (!(map == heap->raw_unchecked_context_map() ||
+          map == heap->raw_unchecked_catch_context_map() ||
+          map == heap->raw_unchecked_global_context_map())) {
       return false;
     }
 
     Context* context = reinterpret_cast<Context*>(ctx);
 
     if (IsJSBuiltinsObject(context->global())) {
       return false;
     }
 
     return true;
@@ skipping 2382 matching lines @@
 }
 
 
 void MarkCompactCollector::Initialize() {
   StaticPointersToNewGenUpdatingVisitor::Initialize();
   StaticMarkingVisitor::Initialize();
 }
 
 
 } }  // namespace v8::internal