Fix top level type inference for binary operators.

pkg/analyzer/test/src/context/mock_sdk.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.test.src.context.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/context/context.dart';
@@ skipping 159 matching lines @@
 
 abstract class num implements Comparable<num> {
   bool operator ==(Object other);
   bool operator <(num other);
   bool operator <=(num other);
   bool operator >(num other);
   bool operator >=(num other);
   num operator +(num other);
   num operator -(num other);
   num operator *(num other);
-  num operator /(num other);
+  double operator /(num other);
   int operator ^(int other);
   int operator |(int other);
   int operator <<(int other);
   int operator >>(int other);
   int operator ~/(num other);
   num operator %(num other);
   int operator ~();
   num operator -();
   int toInt();
   double toDouble();
@@ skipping 440 matching lines @@
 
   @override
   AnalysisCache createCacheFromSourceFactory(SourceFactory factory) {
     if (factory == null) {
       return super.createCacheFromSourceFactory(factory);
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }