Bug 1301514 - Clarify ownership of BrowserElementIsReady. r=kanru

It wasn't immediately obvious to me that BrowserElementIsReady was correctly
guarding against re-running the browser element scripts in a frame.  After more
testing, it was working, but I've added some debug lines for future clarity.
No functionality changes in this patch.

MozReview-Commit-ID: CW4o2TsGKmj

--HG--
extra : rebase_source : 62ec06d4b75f90b3478e403906efaa2f3c3658e2

dom/browser-element/BrowserElementChild.js

@@ -33,8 +33,12 @@ function isTopBrowserElement(docShell) {
   return true;
 }
 
+var BrowserElementIsReady;
+
+debug(`Might load BE scripts: BEIR: ${BrowserElementIsReady}`);
 if (!BrowserElementIsReady) {
-  if (!('BrowserElementIsPreloaded' in this)) {
+  debug("Loading BE scripts")
+  if (!("BrowserElementIsPreloaded" in this)) {
     if (isTopBrowserElement(docShell)) {
       if (Services.prefs.getBoolPref("dom.mozInputMethod.enabled")) {
         try {
@@ -73,8 +77,9 @@ if (!BrowserElementIsReady) {
       ContentPanning.init();
     }
   }
+  BrowserElementIsReady = true;
+} else {
+  debug("BE already loaded, abort");
 }
 
-var BrowserElementIsReady = true;
-
 sendAsyncMessage('browser-element-api:call', { 'msg_name': 'hello' });

dom/browser-element/BrowserElementChildPreload.js

@@ -10,7 +10,7 @@ function debug(msg) {
 
 debug("loaded");
 
-var BrowserElementIsReady = false;
+var BrowserElementIsReady;
 
 var { classes: Cc, interfaces: Ci, results: Cr, utils: Cu }  = Components;
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
@@ -37,8 +37,9 @@ const Timer = Components.Constructor("@mozilla.org/timer;1",
 function sendAsyncMsg(msg, data) {
   // Ensure that we don't send any messages before BrowserElementChild.js
   // finishes loading.
-  if (!BrowserElementIsReady)
+  if (!BrowserElementIsReady) {
     return;
+  }
 
   if (!data) {
     data = { };
@@ -51,8 +52,9 @@ function sendAsyncMsg(msg, data) {
 function sendSyncMsg(msg, data) {
   // Ensure that we don't send any messages before BrowserElementChild.js
   // finishes loading.
-  if (!BrowserElementIsReady)
+  if (!BrowserElementIsReady) {
     return;
+  }
 
   if (!data) {
     data = { };