Shorten long pathnames in page title

Split the path at the last slash to provide only the basename as the
page title in diff-view.

Bug: Issue 4955
Change-Id: I242d38f5823415a53f837ad7d1a5b97bd16c6fa6
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
index 9815983..4d66fe1 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
@@ -602,7 +602,7 @@
       } else if (path === MERGE_LIST_PATH) {
         return 'Merge list';
       }
-      return path;
+      return path.split('/').pop();
     },
 
     _computeTruncatedFileDisplayName(path) {
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 10be37a..0485491 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
@@ -338,7 +338,9 @@
             '42-wheatley.md-10-PARENT');
 
         assert.equal(element._computeFileDisplayName('/foo/bar/baz'),
-            '/foo/bar/baz');
+            'baz');
+        assert.equal(element._computeFileDisplayName('/foobarbaz'),
+            'foobarbaz');
         assert.equal(element._computeFileDisplayName('/COMMIT_MSG'),
             'Commit message');
         assert.equal(element._computeFileDisplayName('/MERGE_LIST'),