Fix PolyGerrit URLs to support prefixed URL

This updates most of polygerrit links to use the implementation added in
I2b2d704fe33c90ea2f2a2183fc79897642a48175 .

Change-Id: Ib3bb694969e903fd76a1dad13cfb642bde086142

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

@@ -14,6 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 -->
 
+<link rel="import" href="../../../behaviors/base-url-behavior/base-url-behavior.html">
 <link rel="import" href="../../../bower_components/polymer/polymer.html">
 <link rel="import" href="../../../bower_components/iron-dropdown/iron-dropdown.html">
 <link rel="import" href="../../shared/gr-button/gr-button.html">

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

@@ -56,6 +56,10 @@
       _hasAvatars: String,
     },
 
+    behaviors: [
+      Gerrit.BaseUrlBehavior,
+    ],
+
     attached: function() {
       this.$.restAPI.getConfig().then(function(cfg) {
         this._hasAvatars = !!(cfg && cfg.plugin && cfg.plugin.has_avatars);
@@ -79,7 +83,7 @@
     },
 
     _computeURLHelper: function(host, path) {
-      return '//' + host + path;
+      return '//' + host + this.getBaseUrl() + path;
     },
 
     _computeRelativeURL: function(path) {