Speed up quoting of JSON strings by allocating a string that is big enough...

src/spaces-inl.h

 // 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 463 matching lines @@
   Page* page = Page::FromAddress(RoundUp(address(), Page::kPageSize));
   return page->ObjectAreaStart();
 }
 
 
 void LargeObjectChunk::Free(Executability executable) {
   MemoryAllocator::FreeRawMemory(address(), size(), executable);
 }
 
 // -----------------------------------------------------------------------------
-// LargeObjectSpace
+// NewSpace
 
 MaybeObject* NewSpace::AllocateRawInternal(int size_in_bytes,
                                            AllocationInfo* alloc_info) {
   Address new_top = alloc_info->top + size_in_bytes;
   if (new_top > alloc_info->limit) return Failure::RetryAfterGC();
 
   Object* obj = HeapObject::FromAddress(alloc_info->top);
   alloc_info->top = new_top;
 #ifdef DEBUG
   SemiSpace* space =
       (alloc_info == &allocation_info_) ? &to_space_ : &from_space_;
   ASSERT(space->low() <= alloc_info->top
          && alloc_info->top <= space->high()
          && alloc_info->limit == space->high());
 #endif
   return obj;
 }
 
 
+template <typename StringType>
+void NewSpace::ShrinkStringAtAllocationBoundary(String* string, int length) {
+  ASSERT(length <= string->length());
+  ASSERT(string->IsSeqString());
+  ASSERT(string->address() + StringType::SizeFor(string->length()) ==
+         allocation_info_.top);
+  allocation_info_.top =
+      string->address() + StringType::SizeFor(length);
+  string->set_length(length);
+}
+
+
 bool FreeListNode::IsFreeListNode(HeapObject* object) {
   return object->map() == Heap::raw_unchecked_byte_array_map()
       || object->map() == Heap::raw_unchecked_one_pointer_filler_map()
       || object->map() == Heap::raw_unchecked_two_pointer_filler_map();
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_INL_H_