Cleanups: addressed your comments from https://codereview.chromium.org/14962008/

runtime/lib/double.cc

 // Copyright (c) 2011, 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 <math.h>
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/code_generator.h"  // DartModulo.
@@ skipping 62 matching lines @@
 }
 
 
 static RawInteger* DoubleToInteger(double val, const char* error_msg) {
   if (isinf(val) || isnan(val)) {
     const Array& args = Array::Handle(Array::New(1));
     args.SetAt(0, String::Handle(String::New(error_msg)));
     Exceptions::ThrowByType(Exceptions::kUnsupported, args);
   }
   const Bigint& big = Bigint::Handle(BigintOperations::NewFromDouble(val));
-  if (BigintOperations::FitsIntoMint(big)) {
-    return Integer::New(BigintOperations::ToMint(big));
+  if (BigintOperations::FitsIntoInt64(big)) {
+    return Integer::New(BigintOperations::ToInt64(big));
   } else {
     return big.raw();
   }
 }
 
 DEFINE_NATIVE_ENTRY(Double_trunc_div, 2) {
   double left = Double::CheckedHandle(arguments->NativeArgAt(0)).value();
   GET_NON_NULL_NATIVE_ARGUMENT(Double, right_object, arguments->NativeArgAt(1));
   double right = right_object.value();
   if (FLAG_trace_intrinsified_natives) {
@@ skipping 261 matching lines @@
 
 DEFINE_NATIVE_ENTRY(Double_getIsNegative, 1) {
   const Double& arg = Double::CheckedHandle(arguments->NativeArgAt(0));
   // Include negative zero, infinity.
   return Bool::Get(signbit(arg.value()) && !isnan(arg.value()));
 }
 
 // Add here only functions using/referring to old-style casts.
 
 }  // namespace dart