Improve SeqString::Truncate for latest allocated strings.

src/spaces.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 2401 matching lines @@
   inline bool FromSpaceContains(Object* o) { return from_space_.Contains(o); }
 
   // Try to switch the active semispace to a new, empty, page.
   // Returns false if this isn't possible or reasonable (i.e., there
   // are no pages, or the current page is already empty), or true
   // if successful.
   bool AddFreshPage();
 
   virtual bool ReserveSpace(int bytes);
 
-  // Resizes a sequential string which must be the most recent thing that was
-  // allocated in new space.
-  template <typename StringType>
-  inline void ShrinkStringAtAllocationBoundary(String* string, int len);
-
 #ifdef VERIFY_HEAP
   // Verify the active semispace.
   virtual void Verify();
 #endif
 
 #ifdef DEBUG
   // Print the active semispace.
   virtual void Print() { to_space_.Print(); }
 #endif
 
@@ skipping 57 matching lines @@
   intptr_t inline_allocation_limit_step_;
 
   Address top_on_previous_step_;
 
   HistogramInfo* allocated_histogram_;
   HistogramInfo* promoted_histogram_;
 
   MUST_USE_RESULT MaybeObject* SlowAllocateRaw(int size_in_bytes);
 
   friend class SemiSpaceIterator;
+  friend void SeqString::Truncate(int new_length);
 
  public:
   TRACK_MEMORY("NewSpace")
 };
 
 
 // -----------------------------------------------------------------------------
 // Old object space (excluding map objects)
 
 class OldSpace : public PagedSpace {
@@ skipping 317 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_