added storage.local.remove

lib/browser-polyfill/chrome-browser-polyfill.js

@@ -244,6 +244,15 @@
 								resolve();
 							}
 						});
+					}),
+					remove: keys => new Promise((resolve, reject) => {
+						nativeAPI.storage.local.remove(keys, () => {
+							if (nativeAPI.runtime.lastError) {
+								reject(nativeAPI.runtime.lastError);
+							} else {
+								resolve();
+							}
+						});
 					})
 				}
 			},