Improve _toInt64() and _toUint64() conversions in TypedData.

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 17095 matching lines @@
     chars[j] = tmp;
     i++;
     j--;
   }
   chars[pos] = '\0';
   return chars;
 }
 
 
 const char* Bigint::ToHexCString(uword (*allocator)(intptr_t size)) const {
-  NoGCScope no_gc;  // TODO(regis): Is this necessary?
-
   const intptr_t used = Used();
   if (used == 0) {
     const char* zero = "0x0";
     const size_t len = strlen(zero) + 1;
     char* chars = reinterpret_cast<char*>(allocator(len));
     strncpy(chars, zero, len);
     return chars;
   }
   const int kBitsPerHexDigit = 4;
   const int kHexDigitsPerDigit = 8;
@@ skipping 3488 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart