Add an interface for retrieving the value of unsigned 64-bit integers.

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index 02c8a41db56d4b9d173e6ce57b6bed8a3902a549..9927c1a79e310a0749dd7e8a2f17bd3440af2a67 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -37,7 +37,7 @@ static const char* MapLibraryUrl(CommandLineOptions* url_mapping,
 int64_t DartUtils::GetIntegerValue(Dart_Handle value_obj) {
   ASSERT(Dart_IsInteger(value_obj));
   int64_t value = 0;
-  Dart_Handle result = Dart_IntegerValue(value_obj, &value);
+  Dart_Handle result = Dart_IntegerToInt64(value_obj, &value);
   ASSERT(!Dart_IsError(result));
   return value;
 }