Fix two deallocation bugs identified by Coverity Prevent....

src/string-stream.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 39 matching lines @@
  public:
   ~HeapStringAllocator() { DeleteArray(space_); }
   char* allocate(unsigned bytes);
   char* grow(unsigned* bytes);
  private:
   char* space_;
 };
 
 
 // Allocator for use when no new c++ heap allocation is allowed.
-// Allocates all space up front and does no allocation while building
-// message.
+// Given a preallocated buffer up front and does no allocation while
+// building message.
 class NoAllocationStringAllocator: public StringAllocator {
  public:
-  explicit NoAllocationStringAllocator(unsigned bytes);
   NoAllocationStringAllocator(char* memory, unsigned size);
   char* allocate(unsigned bytes) { return space_; }
   char* grow(unsigned* bytes);
  private:
   unsigned size_;
   char* space_;
 };
 
 
 class FmtElm {
@@ skipping 114 matching lines @@
   bool full() const { return (capacity_ - length_) == 1; }
   int space() const { return capacity_ - length_; }
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(StringStream);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_STRING_STREAM_H_