Bug 1391218 - Fix 'getDocShellEnumerator is not a function' exception when closing the last tab in a window. r=ochameau

MozReview-Commit-ID: FUcCCljVClI

--HG--
extra : rebase_source : f5bc4f9c88ec17787ac72c053073e8cbbfdf748a

devtools/server/actors/chrome.js

@@ -104,8 +104,10 @@ ChromeActor.prototype.observe = function (subject, topic, data) {
   if (!this.attached) {
     return;
   }
+
+  subject.QueryInterface(Ci.nsIDocShell);
+
   if (topic == "chrome-webnavigation-create") {
-    subject.QueryInterface(Ci.nsIDocShell);
     this._onDocShellCreated(subject);
   } else if (topic == "chrome-webnavigation-destroy") {
     this._onDocShellDestroy(subject);

devtools/server/actors/tab.js

@@ -685,8 +685,10 @@ TabActor.prototype = {
     if (!this.attached) {
       return;
     }
+
+    subject.QueryInterface(Ci.nsIDocShell);
+
     if (topic == "webnavigation-create") {
-      subject.QueryInterface(Ci.nsIDocShell);
       this._onDocShellCreated(subject);
     } else if (topic == "webnavigation-destroy") {
       this._onDocShellDestroy(subject);