feat(build): enforce mobile layout during e2e tests

This is important as we run our benchmarks on
mobile devices as web driver tests fails if buttons
are not visible / overlaid by other content.

modules/benchmarks_external/e2e_test/naive_infinite_scroll_perf.es6

@@ -13,8 +13,8 @@ describe('ng-dart1.x naive infinite scroll benchmark', function () {
         url: URL,
         id: 'ng1-dart1.x.naive_infinite_scroll',
         work: function() {
-          element(by.deepCss('#reset-btn')).click();
-          element(by.deepCss('#run-btn')).click();
+          $('#reset-btn').click();
+          $('#run-btn').click();
           var s = 1000;
           if (appSize > 4) {
             s = s + appSize * 100;

modules/benchmarks_external/src/naive_infinite_scroll/app.dart

@@ -11,10 +11,6 @@ import 'package:angular2/src/test_lib/benchmark_util.dart';
     <div>
         <div style="display: flex">
           <scroll-area scroll-top="scrollTop"></scroll-area>
-          <div style="padding-left: 20px">
-            <button id='run-btn'>Run</button>
-            <button id='reset-btn'>Reset</button>
-          </div>
         </div>
         <div ng-if="scrollAreas.length > 0">
           <p>Following tables are only here to add weight to the UI:</p>
@@ -39,10 +35,10 @@ class App implements ShadowRootAware {
 
   @override
   void onShadowRoot(ShadowRoot shadowRoot) {
-    bindAction('scroll-app /deep/ #run-btn', () {
+    bindAction('#run-btn', () {
       runBenchmark();
     });
-    bindAction('scroll-app /deep/ #reset-btn', () {
+    bindAction('#reset-btn', () {
       scrollTop = 0;
     });
   }

modules/benchmarks_external/src/naive_infinite_scroll/index.html

@@ -9,6 +9,10 @@
     Iteration count: <input type="text" name="iterationCount" value="1"></input><br>
     Scroll increment: <input type="text" name="scrollIncrement" value="1"></input><br>
   </form>
+  <div>
+    <button id="run-btn">Run</button>
+    <button id="reset-btn">Reset</button>
+  </div>
   <scroll-app></scroll-app>
 
   $SCRIPTS$