GuestView: Only update contentWindow on attach if not null

If BrowserPlugin goes away (e.g. display:none) then queued callbacks will be executed undefined
parameters so that guest_view.js' queue can advance. We need to make sure that we don't clear
the contentWindow in this case so that it is possible to continue messaging the guest after display:none.

BUG=471757

Review URL: https://codereview.chromium.org/1050603002

Cr-Commit-Position: refs/heads/master@{#323088}

1 files changed, 4 insertions, 3 deletions

diff --git a/extensions/renderer/resources/guest_view/guest_view.js b/extensions/renderer/resources/guest_view/guest_view.js
index 433d69b..27368a4 100644
--- a/extensions/renderer/resources/guest_view/guest_view.js
+++ b/extensions/renderer/resources/guest_view/guest_view.js
@@ -143,12 +143,13 @@ GuestViewImpl.prototype.attachImpl = function(
   // callback, handle potential attaching failure, register an automatic detach,
   // and advance the queue.
   var callbackWrapper = function(callback, contentWindow) {
-    this.contentWindow = contentWindow;
-
     // Check if attaching failed.
-    if (!this.contentWindow) {
+    if (!contentWindow) {
       this.state = GUEST_STATE_CREATED;
       this.internalInstanceId = 0;
+    } else {
+      // Only update the contentWindow if attaching is successful.
+      this.contentWindow = contentWindow;
     }
 
     this.handleCallback(callback);