Fix Request Interception (#565)

It turned out that either Network.requestIntercepted or
Network.requestWillBeSent occasionally report encoded URL.

This patch starts decoding URL's when generating request hash.

Fixes #558.

lib/Multimap.js

@@ -122,6 +122,13 @@ class Multimap {
     return result;
   }
 
+  /**
+   * @return {!Array<!K>}
+   */
+  keysArray() {
+    return Array.from(this._map.keys());
+  }
+
   clear() {
     this._map.clear();
   }