Upgrade gr-dropdown for download links

Bug: Issue 7867
Change-Id: I80803e388862872cb059c7f7ec0c269ce6a80755

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

@@ -145,6 +145,7 @@ limitations under the License.
                 <a
                     class="itemAction"
                     href$="[[_computeLinkURL(link)]]"
+                    download$="[[_computeIsDownload(link)]]"
                     rel$="[[_computeLinkRel(link)]]"
                     target$="[[link.target]]"
                     hidden$="[[!link.url]]"

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

@@ -286,5 +286,9 @@
     _computeHasTooltip(tooltip) {
       return !!tooltip;
     },
+
+    _computeIsDownload(link) {
+      return !!link.download;
+    },
   });
 })();

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

@@ -49,6 +49,11 @@ limitations under the License.
       sandbox.restore();
     });
 
+    test('_computeIsDownload', () => {
+      assert.isTrue(element._computeIsDownload({download: true}));
+      assert.isFalse(element._computeIsDownload({download: false}));
+    });
+
     test('tap on trigger opens menu, then closes', () => {
       sandbox.stub(element, '_open', () => { element.$.dropdown.open(); });
       sandbox.stub(element, '_close', () => { element.$.dropdown.close(); });