Update GWT footer link to be page specific

Previously, the GWT UI link at the bottom of every page linked to the
Gerrit GWT homepage. This change updates the path of that link whenever
the location-change event is fired.

Bug: Issue 4619
Change-Id: Iddbd83fddec750c165831c673a0e3394318c4ae2

polygerrit-ui/app/elements/gr-app.html

@@ -129,7 +129,7 @@ limitations under the License.
           target="_blank">Report PolyGerrit Bug</a>
       <template is="dom-if" if="[[_computeShowGwtUiLink(_serverConfig)]]">
         |
-        <a href="/?polygerrit=0" rel="external">GWT UI</a>
+        <a id="gwtLink" href$="/?polygerrit=0#[[_path]]" rel="external">GWT UI</a>
       </template>
     </footer>
     <gr-overlay id="keyboardShortcuts" with-backdrop>

polygerrit-ui/app/elements/gr-app.js

@@ -43,11 +43,13 @@
       _showSettingsView: Boolean,
       _viewState: Object,
       _lastError: Object,
+      _path: String,
     },
 
     listeners: {
       'page-error': '_handlePageError',
       'title-change': '_handleTitleChange',
+      'location-change': '_handleLocationChange',
     },
 
     observers: [
@@ -158,6 +160,15 @@
       }
     },
 
+    _handleLocationChange: function() {
+      var hash = location.hash.substring(1);
+      var pathname = location.pathname;
+      if (pathname.startsWith('/c/') && parseInt(hash, 10) > 0) {
+        pathname += '@' + hash;
+      }
+      this.set('_path', encodeURIComponent(pathname));
+    },
+
     _handleTitleChange: function(e) {
       if (e.detail.title) {
         document.title = e.detail.title + ' · Gerrit Code Review';

polygerrit-ui/app/elements/gr-app_test.html

@@ -39,6 +39,14 @@ limitations under the License.
       stub('gr-reporting', {
         appStarted: sandbox.stub(),
       });
+      var config = {
+        gerrit: {web_uis: ['GWT', 'POLYGERRIT']},
+        plugin: {js_resource_paths: []},
+      };
+      stub('gr-rest-api-interface', {
+        getConfig: function() { return Promise.resolve(config); },
+      });
+
       element = fixture('basic');
       flush(done);
     });
@@ -49,5 +57,12 @@ limitations under the License.
     test('reporting', function() {
       assert.isTrue(element.$.reporting.appStarted.calledOnce);
     });
+
+    test('location change updates gwt footer', function() {
+      element._path = '/test/path';
+      var gwtLink = element.$$('#gwtLink');
+      assert.equal(gwtLink.href,
+          'http://' + location.host + '/?polygerrit=0#/test/path');
+    });
   });
 </script>