Respond to Ivan's code review comments from previous TBR cl.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 13672 matching lines @@
         *(CharAddr(dststr, index)) = '\\';
         *(CharAddr(dststr, index + 1)) = SpecialCharacter(*CharAddr(str, i));
         index += 2;
       } else {
         *(CharAddr(dststr, index)) = *CharAddr(str, i);
         index += 1;
       }
     }
     return OneByteString::raw(dststr);
   }
-  return OneByteString::New(static_cast<intptr_t>(0), Heap::kNew);
+  return OneByteString::raw(Symbols::Empty());
 }
 
 RawOneByteString* ExternalOneByteString::EscapeSpecialCharacters(
     const String& str) {
   intptr_t len = str.Length();
   if (len > 0) {
     intptr_t num_escapes = 0;
     for (intptr_t i = 0; i < len; i++) {
       if (IsSpecialCharacter(*CharAddr(str, i))) {
         num_escapes += 1;
       }
     }
     const String& dststr = String::Handle(
         OneByteString::New(len + num_escapes, Heap::kNew));
     intptr_t index = 0;
     for (intptr_t i = 0; i < len; i++) {
       if (IsSpecialCharacter(*CharAddr(str, i))) {
         *(OneByteString::CharAddr(dststr, index)) = '\\';
         *(OneByteString::CharAddr(dststr, index + 1)) =
         SpecialCharacter(*CharAddr(str, i));
         index += 2;
       } else {
         *(OneByteString::CharAddr(dststr, index)) = *CharAddr(str, i);
         index += 1;
       }
     }
     return OneByteString::raw(dststr);
   }
-  return OneByteString::New(static_cast<intptr_t>(0), Heap::kNew);
+  return OneByteString::raw(Symbols::Empty());
 }
 
 
 RawOneByteString* OneByteString::New(intptr_t len,
                                      Heap::Space space) {
   ASSERT(Isolate::Current() == Dart::vm_isolate() ||
          Isolate::Current()->object_store()->one_byte_string_class() !=
          Class::null());
   if (len < 0 || len > kMaxElements) {
     // This should be caught before we reach here.
@@ skipping 1504 matching lines @@
   return "_MirrorReference";
 }
 
 
 void MirrorReference::PrintToJSONStream(JSONStream* stream, bool ref) const {
   JSONObject jsobj(stream);
 }
 
 
 }  // namespace dart