unlock device and pass JAVA_HOME to instrumentation test (#11174)

dev/devicelab/bin/tasks/flutter_gallery_instrumentation_test.dart

@@ -16,9 +16,15 @@ Future<Null> main() async {
     final Directory galleryDirectory =
       dir('${flutterDirectory.path}/examples/flutter_gallery');
     await inDirectory(galleryDirectory, () async {
+      final Device device = await devices.workingDevice;
+      await device.unlock();
       await flutter('packages', options: <String>['get']);
-      await flutter('build', options: <String>['clean']);  // to reset the Dart entry point
-      await exec('tool/run_instrumentation_test.sh', <String>[]);
+      await flutter('build', options: <String>['clean']);
+      await flutter('build', options: <String>['apk', '--target', 'test/live_smoketest.dart']);
+      final String androidStudioPath = grep('Android Studio at', from: await evalFlutter('doctor')).first.split(' ').last;
+      await exec('./tool/run_instrumentation_test.sh', <String>[], environment: <String, String>{
+        'JAVA_HOME': '$androidStudioPath/jre',
+      });
     });
 
     return new TaskResult.success(null);