Disable WebShare on platforms other than android.

third_party/WebKit/LayoutTests/webshare/resources/mock-share-service.js

 'use strict';
 
 let mockShareService = loadMojoModules(
     'mockShareService',
     ['mojo/public/js/router',
      'third_party/WebKit/public/platform/modules/webshare/webshare.mojom',
     ]).then(mojo => {
   let [router, webshare] = mojo.modules;
 
   class MockShareService extends webshare.ShareService.stubClass {
@@ skipping 49 matching lines @@
 
 function share_test(func, name, properties) {
   promise_test(t => mockShareService.then(mock => {
     let mockPromise = mock.init_();
     return Promise.race([func(t, mock), mockPromise]);
   }), name, properties);
 }
 
 // Copied from resources/bluetooth/bluetooth-helpers.js.
 function callWithKeyDown(functionCalledOnKeyPress) {
-  return new Promise(resolve => {
+  return new Promise((resolve, reject) => {
     function onKeyPress() {
       document.removeEventListener('keypress', onKeyPress, false);
-      resolve(functionCalledOnKeyPress());
+      try {
+        resolve(functionCalledOnKeyPress());
+      } catch (e) {
+        reject(e);
+      }
     }
     document.addEventListener('keypress', onKeyPress, false);
 
     eventSender.keyDown(' ', []);
   });
 }