Stop using a prebuilt APK

Instead, require an AndroidManifest.xml and always build an APK.

Fixes #2517

packages/flutter_tools/test/src/mocks.dart

diff --git a/packages/flutter_tools/test/src/mocks.dart b/packages/flutter_tools/test/src/mocks.dart
index 62d6c36..52db59e 100644
--- a/packages/flutter_tools/test/src/mocks.dart
+++ b/packages/flutter_tools/test/src/mocks.dart
@@ -16,7 +16,11 @@
 
 class MockApplicationPackageStore extends ApplicationPackageStore {
   MockApplicationPackageStore() : super(
-    android: new AndroidApk(localPath: '/mock/path/to/android/SkyShell.apk'),
+    android: new AndroidApk(
+      localPath: '/mock/path/to/android/SkyShell.apk',
+      id: 'io.flutter.android.mock',
+      launchActivity: 'io.flutter.android.mock.MockActivity'
+    ),
     iOS: new IOSApp(
       iosProjectDir: '/mock/path/to/iOS/SkyShell.app',
       iosProjectBundleId: 'io.flutter.ios.mock'