Bug 1107443 part 5. Fix the addon SDK to not try defining non-configurable properties on content windows. r=mossop

addon-sdk/source/lib/sdk/content/sandbox.js

@@ -193,7 +193,8 @@ const WorkerSandbox = Class({
     // `addon` in document is equivalent to `self` in content script.
     if (requiresAddonGlobal(worker)) {
       Object.defineProperty(getUnsafeWindow(window), 'addon', {
-          value: content.self
+          value: content.self,
+          configurable: true
         }
       );
     }

addon-sdk/source/lib/sdk/deprecated/traits-worker.js

@@ -238,7 +238,8 @@ const WorkerSandbox = EventEmitter.compose({
     if (worker._injectInDocument) {
       let win = window.wrappedJSObject ? window.wrappedJSObject : window;
       Object.defineProperty(win, "addon", {
-          value: content.self
+          value: content.self,
+          configurable: true
         }
       );
     }