Fix all Observatory warnings/errors.

runtime/observatory/test/debugging_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 --checked
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 import 'dart:async';
 
@@ skipping 38 matching lines @@
   });
   isolate.resume();
   return completer.future;
 },
 
 // Add breakpoint
 (Isolate isolate) {
   return isolate.rootLib.load().then((_) {
       // Set up a listener to wait for breakpoint events.
       Completer completer = new Completer();
-      List events = [];
       var subscription;
       subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
         if (event.eventType == ServiceEvent.kPauseBreakpoint) {
           print('Breakpoint reached');
           subscription.cancel();
           completer.complete();
         }
       });
 
       // Add the breakpoint.
@@ skipping 17 matching lines @@
       expect(stack['frames'].length, greaterThanOrEqualTo(1));
       expect(stack['frames'][0]['function'].name, equals('testFunction'));
       expect(stack['frames'][0]['tokenPos'], equals(58));
   });
 },
 
 // Stepping
 (Isolate isolate) {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
-  List events = [];
   var subscription;
   subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
     if (event.eventType == ServiceEvent.kPauseBreakpoint) {
       print('Breakpoint reached');
       subscription.cancel();
       completer.complete();
     }
   });
 
   return isolate.stepInto().then((isolate) {
     return completer.future;  // Wait for breakpoint events.
   });
 },
 
 // Get the stack trace again.  Our position has updated.
 (Isolate isolate) {
   return isolate.getStack().then((ServiceMap stack) {
       expect(stack.type, equals('Stack'));
       expect(stack['frames'].length, greaterThanOrEqualTo(2));
       expect(stack['frames'][0]['function'].name, equals('testFunction'));
       expect(stack['frames'][0]['tokenPos'], equals(60));
   });
 },
 
 // Remove breakpoint
 (Isolate isolate) {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
-  List events = [];
   var subscription;
   subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
     if (event.eventType == ServiceEvent.kBreakpointRemoved) {
       print('Breakpoint removed');
       expect(isolate.breakpoints.length, equals(0));
       subscription.cancel();
       completer.complete();
     }
   });
 
@@ skipping 15 matching lines @@
     }
   });
   isolate.resume();
   return completer.future;
 },
 
 // Add breakpoint at function entry
 (Isolate isolate) {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
-  List events = [];
   var subscription;
   subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
     if (event.eventType == ServiceEvent.kPauseBreakpoint) {
       print('Breakpoint reached');
       subscription.cancel();
       completer.complete();
     }
   });
 
   // Find a specific function.
   ServiceFunction function = isolate.rootLib.functions.firstWhere(
       (f) => f.name == 'helper');
   expect(function, isNotNull);
 
   // Add the breakpoint at function entry
   return isolate.addBreakpointAtEntry(function).then((result) {
     expect(result is Breakpoint, isTrue);
     Breakpoint bpt = result;
     expect(bpt.type, equals('Breakpoint'));
     expect(bpt.script.name, equals('debugging_test.dart'));
     expect(bpt.tokenPos, equals(29));
     expect(isolate.breakpoints.length, equals(1));
     return completer.future;  // Wait for breakpoint events.
   });
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeConcurrent: testFunction);