Fix analyzer warnings

We were just missing a few type casts in tests to make the analyzer happy.

packages/flutter/lib/src/widgets/transitions.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:sky/animation.dart';
-import 'package:sky/src/widgets/animated_component.dart';
 import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/framework.dart';
 import 'package:sky/src/widgets/global_key_watcher.dart';

packages/unit/test/services/mock_services.dart

@@ -10,7 +10,7 @@ class _ServiceMocker {
   // Map of interface names to mock implementations.
   Map<String, Object> _interfaceMock = new Map<String, Object>();
 
-  bool _requestService(String url, Object proxy) {
+  bool _requestService(String url, dynamic proxy) {
     Object mock = _interfaceMock[proxy.impl.name];
     if (mock != null) {
       // Replace the proxy's implementation of the service interface with the

packages/unit/test/widget/input_test.dart

 import 'package:mojo_services/keyboard/keyboard.mojom.dart';
+import 'package:sky/rendering.dart';
 import 'package:sky/services.dart';
 import 'package:sky/widgets.dart';
 import 'package:test/test.dart';
@@ -9,7 +10,7 @@ import '../services/mock_services.dart';
 class MockKeyboard implements KeyboardService {
   KeyboardClient client;
 
-  void show(Object client, int type) {
+  void show(KeyboardClientStub client, int type) {
     this.client = client.impl;
   }
 
@@ -41,7 +42,7 @@ void main() {
     tester.pumpFrame(builder);
 
     Input input = tester.findWidget((Widget widget) => widget.key == inputKey);
-    Size emptyInputSize = input.renderObject.size;
+    Size emptyInputSize = (input.renderObject as RenderBox).size;
 
     // Simulate entry of text through the keyboard.
     expect(mockKeyboard.client, isNotNull);
@@ -54,6 +55,6 @@ void main() {
     tester.pumpFrame(builder);
 
     // Check that the Input with text has the same size as the empty Input.
-    expect(input.renderObject.size, equals(emptyInputSize));
+    expect((input.renderObject as RenderBox).size, equals(emptyInputSize));
   });
 }