Show "File X of Y" next to file navigation links in diff view

Bug: Issue 4917
Change-Id: Ie993504fe80034da0e3d3ddee99687ba09ebc2ff

polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html

diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
index 4daabe3..4565338 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
@@ -876,6 +876,19 @@
       assert.isTrue(callCompute({basePatchNum: 1, patchNum: 'edit'}));
     });
 
+    test('_computeFileNum', () => {
+      assert.equal(element._computeFileNum('/foo',
+          [{value: '/foo'}, {value: '/bar'}]), 1);
+      assert.equal(element._computeFileNum('/bar',
+          [{value: '/foo'}, {value: '/bar'}]), 2);
+    });
+
+    test('_computeFileNumVisible', () => {
+      assert.equal(element._computeFileNumVisible('', []), 'hidden');
+      assert.equal(element._computeFileNumVisible('/bar',
+          [{value: '/foo'}, {value: '/bar'}]), '');
+    });
+
     suite('editMode behavior', () => {
       setup(() => {
         element._loggedIn = true;