Issue 4579 - Ignore runtime.lastError caused by wrapper

polyfill.js

Index: polyfill.js
===================================================================
--- a/polyfill.js
+++ b/polyfill.js
@@ -38,16 +38,22 @@
     "tabs.sendMessage",
     "tabs.update",
     "webNavigation.getAllFrames",
     "webRequest.handlerBehaviorChanged",
     "windows.create",
     "windows.update"
   ];
 
+  // Errors that occur only when we show an interest in the response from an
+  // API call.
+  const noFulfillmentErrors = new Set([
+    "The message port closed before a response was received."
+  ]);
+
   function wrapAPI(api)
   {
     let object = browser;
     let path = api.split(".");
     let name = path.pop();
 
     for (let node of path)
     {
@@ -71,17 +77,17 @@
       if (typeof args[args.length - 1] == "undefined")
         args.pop();
 
       return new Promise((resolve, reject) =>
       {
         func.call(object, ...args, result =>
         {
           let error = browser.runtime.lastError;
-          if (error)
+          if (error && !noFulfillmentErrors.has(error.message))
             reject(error);
           else
             resolve(result);
         });
       });
     };
   }