Moved mock-diff-response and fix flaky tests

Moved the mock-diff-response test element to a more-appropriate location
and fixed two tests that were flaky in Safari.

Change-Id: I927973319b200021592b0c9e18c04a902f643894

polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager_test.html

@@ -50,7 +50,7 @@ limitations under the License.
     test('show auth error', function(done) {
       var showAuthErrorStub = sandbox.stub(element, '_showAuthErrorAlert');
       element.fire('server-error', {response: {status: 403}});
-      flush(function() {
+      element.$.restAPI.getLoggedIn.lastCall.returnValue.then(function() {
         assert.isTrue(showAuthErrorStub.calledOnce);
         done();
       });
@@ -90,7 +90,7 @@ limitations under the License.
       var toastSpy = sandbox.spy(element, '_createToastAlert');
       var windowOpen = sandbox.stub(window, 'open');
       element.fire('server-error', {response: {status: 403}});
-      flush(function() {
+      element.$.restAPI.getLoggedIn.lastCall.returnValue.then(function() {
         assert.isTrue(toastSpy.called);
         var toast = toastSpy.lastCall.returnValue;
         assert.isOk(toast);

polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder_test.html

@@ -25,7 +25,7 @@ limitations under the License.
 <script src="gr-diff-builder.js"></script>
 <script src="../../../scripts/util.js"></script>
 
-<link rel="import" href="../gr-diff-cursor/mock-diff-response_test.html">
+<link rel="import" href="../../shared/gr-rest-api-interface/mock-diff-response_test.html">
 <link rel="import" href="gr-diff-builder.html">
 
 <test-fixture id="basic">

polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html

@@ -25,7 +25,7 @@ limitations under the License.
 <link rel="import" href="../../../bower_components/iron-test-helpers/iron-test-helpers.html">
 <link rel="import" href="../gr-diff/gr-diff.html">
 <link rel="import" href="./gr-diff-cursor.html">
-<link rel="import" href="./mock-diff-response_test.html">
+<link rel="import" href="../../shared/gr-rest-api-interface/mock-diff-response_test.html">
 
 <test-fixture id="basic">
   <template>