Make several service protocol RPCs private.

runtime/observatory/tests/service/metrics_test.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.
 // 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:profiler';
@@ skipping 10 matching lines @@
     Map metrics = await isolate.refreshDartMetrics();
     expect(metrics.length, equals(1));
     var counter = metrics['metrics/a.b.c'];
     expect(counter.name, equals('a.b.c'));
     expect(counter.value, equals(1234.5));
   },
 
   (Isolate isolate) async {
     var params =  { 'metricId': 'metrics/a.b.c' };
     ServiceMetric counter =
-      await isolate.invokeRpc('getIsolateMetric', params);
+      await isolate.invokeRpc('_getIsolateMetric', params);
     expect(counter.name, equals('a.b.c'));
     expect(counter.value, equals(1234.5));
   },
 
   (Isolate isolate) async {
     bool caughtException;
     try {
-      await isolate.invokeRpc('getIsolateMetric',
+      await isolate.invokeRpc('_getIsolateMetric',
                               { 'metricId': 'metrics/a.b.d' });
       expect(false, isTrue, reason:'Unreachable');
     } on ServerRpcException catch (e) {
       caughtException = true;
       expect(e.code, equals(ServerRpcException.kInvalidParams));
       expect(e.message,
-             "getIsolateMetric: invalid 'metricId' parameter: metrics/a.b.d");
+             "_getIsolateMetric: invalid 'metricId' parameter: metrics/a.b.d");
     }
     expect(caughtException, isTrue);
   },
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);