Add polygerrit-ui/app/test/common-test-setup.html

This is a partial roll-forward of c/106190

This replaces all loads of iron-test-helpers with a load of a file
that wraps it, and adds that file to test files that do not currently
load iron-test-helpers.

A future CL will also install polymer-resin via common-test-helpers.html.

I tested by running

$ WCT_ARGS="-l chrome" ./polygerrit-ui/app/run_test.sh

Change-Id: Ifb3cd2c8db13d724f57e56e7e78045470d103a43
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
index 24fee39..53d7345 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
@@ -20,8 +20,7 @@
 
 <script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
 <script src="../../../bower_components/web-component-tester/browser.js"></script>
-
-<link rel="import" href="../../../bower_components/iron-test-helpers/iron-test-helpers.html">
+<link rel="import" href="../../../test/common-test-setup.html"/>
 <!--
 This must refer to the element this interface is wrapping around. Otherwise
 breaking changes to gr-change-actions won’t be noticed.
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
index 3080df1..2f67035 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
@@ -20,8 +20,7 @@
 
 <script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
 <script src="../../../bower_components/web-component-tester/browser.js"></script>
-
-<link rel="import" href="../../../bower_components/iron-test-helpers/iron-test-helpers.html">
+<link rel="import" href="../../../test/common-test-setup.html"/>
 <!--
 This must refer to the element this interface is wrapping around. Otherwise
 breaking changes to gr-reply-dialog won’t be noticed.
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
index 40810b1..761fe2a 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
@@ -20,6 +20,7 @@
 
 <script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
 <script src="../../../bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
 <link rel="import" href="gr-js-api-interface.html">
 
 <script>void(0);</script>