Color statuses in change list items

Adds a "flat" mode to gr-change-status that changes the styling of the
chip to emulate a flat Material button, and uses that element in the
change list.

Bug: Issue 8362
Change-Id: I23814d2d6e291821ed3c8a90d75b0d4a1d2b1ac3

polygerrit-ui/app/elements/shared/gr-change-status/gr-change-status_test.html

diff --git a/polygerrit-ui/app/elements/shared/gr-change-status/gr-change-status_test.html b/polygerrit-ui/app/elements/shared/gr-change-status/gr-change-status_test.html
index 801249d..212296f 100644
--- a/polygerrit-ui/app/elements/shared/gr-change-status/gr-change-status_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-change-status/gr-change-status_test.html
@@ -52,6 +52,15 @@
       assert.isTrue(element.classList.contains('wip'));
     });
 
+    test('WIP flat', () => {
+      element.flat = true;
+      element.status = 'WIP';
+      assert.equal(element.$$('.chip').innerText, 'WIP');
+      assert.isDefined(element.tooltipText);
+      assert.isTrue(element.classList.contains('wip'));
+      assert.isTrue(element.hasAttribute('flat'));
+    });
+
     test('merged', () => {
       element.status = 'Merged';
       assert.equal(element.$$('.chip').innerText, element.status);