Switch to using SourceLocation universally in service protocol.

runtime/observatory/tests/service/code_test.dart

 // Copyright (c) 2015, 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.
 // VMOptions=--compile-all --error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 import 'dart:async';
 
@@ skipping 41 matching lines @@
 
 // Inspect code objects for top two frames.
 (Isolate isolate) {
   return isolate.getStack().then((ServiceMap stack) {
       // Make sure we are in the right place.
       expect(stack.type, equals('Stack'));
       expect(stack['frames'].length, greaterThanOrEqualTo(3));
       var frame0 = stack['frames'][0];
       var frame1 = stack['frames'][1];
       print(frame0);
-      expect(frame0['function'].name, equals('funcB'));
-      expect(frame1['function'].name, equals('funcA'));
-      var codeId0 = frame0['code'].id;
-      var codeId1 = frame1['code'].id;
+      expect(frame0.function.name, equals('funcB'));
+      expect(frame1.function.name, equals('funcA'));
+      var codeId0 = frame0.code.id;
+      var codeId1 = frame1.code.id;
 
       List tests = [];
       // Load code from frame 0.
       tests.add(isolate.getObject(codeId0)..then((Code code) {
             expect(code.type, equals('Code'));
             expect(code.function.name, equals('funcB'));
             expect(code.hasDisassembly, equals(true));
           }));
       // Load code from frame 0.
       tests.add(isolate.getObject(codeId1)..then((Code code) {
             expect(code.type, equals('Code'));
             expect(code.function.name, equals('funcA'));
             expect(code.hasDisassembly, equals(true));
           }));
       return Future.wait(tests);
   });
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeConcurrent: testFunction);