[ios] Test cases for plugin placeholder injection.

BUG=630690

Review-Url: https://codereview.chromium.org/2183543002
Cr-Commit-Position: refs/heads/master@{#408012}
diff --git a/ios/web/ios_web_shell_tests.gyp b/ios/web/ios_web_shell_tests.gyp
index 1a50a2b..794d7cb 100644
--- a/ios/web/ios_web_shell_tests.gyp
+++ b/ios/web/ios_web_shell_tests.gyp
@@ -66,6 +66,7 @@
         'shell/test/meta_tags_egtest.mm',
         'shell/test/navigation_egtest.mm',
         'shell/test/page_state_egtest.mm',
+        'shell/test/plugin_placeholder_egtest.mm',
       ],
       'actions': [{
         'action_name': 'copy_test_data',