Work around for unpredictable content script execution order.

src/content/staticNS.js

@@ -41,8 +41,14 @@
         //, document.domain, document.baseURI, window.isSecureContext // DEV_ONLY
       );
 
-      if (this.syncFetchPolicy) { // ftp: or file: - no CSP headers yet
-        this.syncFetchPolicy();
+      if (/^(ftp|file):/.test(url)) { // ftp: or file: - no CSP headers yet
+        if (this.syncFetchPolicy) {
+          this.syncFetchPolicy();
+        } else { // additional content scripts not loaded yet
+          log("Waiting for syncFetchPolicy to load...");
+          this.pendingFetchPolicy = true;
+          return;
+        }
       } else {
         // CSP headers have been already provided by webRequest, we are not in a hurry...
         if (/^(javascript|about):/.test(url)) {

src/content/syncFetchPolicy.js

@@ -143,4 +143,9 @@
       error("Background page not ready yet, retrying to fetch policy...")
     }
   }
+};
+
+if (this.ns.pendingSyncFetchPolicy) {
+  this.ns.pendingSyncFetchPolicy = false;
+  this.ns.syncFetchPolicy();
 }