Expose sky KeyboardService in android mojo_shell

sky/framework/embedder.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import "package:mojo/public/dart/application.dart";
 import "dart:sky.internals" as internals;
 import "package:mojo/public/dart/bindings.dart" as bindings;
 import "package:mojo/public/dart/core.dart" as core;
 import "package:mojo/service_provider.mojom.dart";
 import "package:mojo/shell.mojom.dart";
 import "package:mojo/service_registry.mojom.dart";
 
 final _EmbedderImpl embedder = new _EmbedderImpl();
 
 class _EmbedderImpl {
   ApplicationConnection _connection;
   ServiceRegistryProxy _serviceRegistry;
+  ShellProxy _shell;
+  bool _internalsHasNoShell = false;
 
-  final ShellProxy shell = new ShellProxy.fromHandle(
-      new core.MojoHandle(internals.takeShellProxyHandle()));
+  ShellProxy get shell {
+    if (_internalsHasNoShell || _shell != null) return _shell;
+
+    try {
+      _shell = new ShellProxy.fromHandle(
+          new core.MojoHandle(internals.takeShellProxyHandle()));
+    } catch (e) {
+      _internalsHasNoShell = true;
+    }
+    return _shell;
+  }
 
   ApplicationConnection get connection {
     if (_connection == null) {
       var stubHandle =
           new core.MojoHandle(internals.takeServicesProvidedToEmbedder());
       var proxyHandle =
           new core.MojoHandle(internals.takeServicesProvidedByEmbedder());
       _connection = new ApplicationConnection(stubHandle.isValid
           ? new ServiceProviderStub.fromHandle(stubHandle)
           : null, proxyHandle.isValid
@@ skipping 20 matching lines @@
   }
 
   ServiceRegistryProxy get serviceRegistry {
     if (_serviceRegistry == null) {
       _serviceRegistry = new ServiceRegistryProxy.fromHandle(
           new core.MojoHandle(internals.takeServiceRegistry()));
     }
     return _serviceRegistry;
   }
 }