Introduce lazy sweeping.

src/heap.h

 // Copyright 2011 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 1158 matching lines @@
   inline bool OldGenerationPromotionLimitReached() {
     return (PromotedSpaceSize() + PromotedExternalMemorySize())
            > old_gen_promotion_limit_;
   }
 
   inline intptr_t OldGenerationSpaceAvailable() {
     return old_gen_allocation_limit_ -
            (PromotedSpaceSize() + PromotedExternalMemorySize());
   }
 
+  inline void LowerOldGenLimits(int bytes) {
+    old_gen_promotion_limit_ -= bytes;
+    old_gen_allocation_limit_ -= bytes;
+  }
+
   // Can be called when the embedding application is idle.
   bool IdleNotification();
 
   // Declare all the root indices.
   enum RootListIndex {
 #define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
     STRONG_ROOT_LIST(ROOT_INDEX_DECLARATION)
 #undef ROOT_INDEX_DECLARATION
 
 // Utility type maps
@@ skipping 1144 matching lines @@
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #undef HEAP
 
 #endif  // V8_HEAP_H_