Revert "Define guest view custom elements synchronously"

This reverts commit 5d01e87e.

Reason for revert: Caused regression https://crbug.com/1014385

Original change's description:
> Define guest view custom elements synchronously
> 
> Previously, we've had to wait for readystatechange before defining
> the guest view custom elements because
> 1) there were circular dependencies that would cause errors if we
> tried to perform the definition immediately, and
> 2) the Custom Elements V0 registration context was scoped to the
> document rather than the window, so if we defined the elements
> while the document was still on about:blank, the definition would
> be available on about:blank, but not for the extension.
> 
> Now that the circular dependencies are fixed and guest view is
> migrated to Custom Elements V1 (whose registration context is
> scoped to the window), it is no longer necessary to wait for
> readystatechange.
> 
> We now perform the definition immediately.
> 
> Bug: 810012
> Change-Id: Ib5e8ba6f4e302eaae56c5566765521d64b1a0e15
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1278287
> Commit-Queue: Kevin McNee <mcnee@chromium.org>
> Reviewed-by: James MacLean <wjmaclean@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#700425}

TBR=wjmaclean@chromium.org,mcnee@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 810012, 1014385
Change-Id: Ie43a88bc07036fc392079cc8f2593e28440de104
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863691Reviewed-by: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706200}

extensions/renderer/resources/guest_view/guest_view_container_element.js

@@ -15,11 +15,20 @@ var GuestViewInternalNatives = requireNative('guest_view_internal');
 var IdGenerator = requireNative('id_generator');
 var logging = requireNative('logging');
 
-// Registers the browserplugin and guestview as custom elements.
+// Registers the browserplugin and guestview as custom elements once the
+// document has loaded.
 // |containerElementType| is a GuestViewContainerElement (e.g. WebViewElement)
 function registerElement(elementName, containerElementType) {
-  registerInternalElement($String.toLowerCase(elementName));
-  registerGuestViewElement(elementName, containerElementType);
+  var useCapture = true;
+  window.addEventListener('readystatechange', function listener(event) {
+    if (document.readyState == 'loading')
+      return;
+
+    registerInternalElement($String.toLowerCase(elementName));
+    registerGuestViewElement(elementName, containerElementType);
+
+    $EventTarget.removeEventListener(window, event.type, listener, useCapture);
+  }, useCapture);
 }
 
 // Registers the browser plugin <object> custom element. |viewType| is the

extensions/renderer/resources/guest_view/guest_view_deny.js

@@ -40,11 +40,19 @@ function registerGuestViewElement(viewType) {
   });
 }
 
-for (var viewType of VIEW_TYPES) {
-  // Register the error-providing custom element only for those view types
-  // that have not already been registered. Since this module is always loaded
-  // last, all the view types that are available (i.e. have the proper
-  // permissions) will have already been registered on |window|.
-  if (!$Object.hasOwnProperty(window, viewType))
-    registerGuestViewElement(viewType);
-}
+var useCapture = true;
+window.addEventListener('readystatechange', function listener(event) {
+  if (document.readyState == 'loading')
+    return;
+
+  for (var viewType of VIEW_TYPES) {
+    // Register the error-providing custom element only for those view types
+    // that have not already been registered. Since this module is always loaded
+    // last, all the view types that are available (i.e. have the proper
+    // permissions) will have already been registered on |window|.
+    if (!$Object.hasOwnProperty(window, viewType))
+      registerGuestViewElement(viewType);
+  }
+
+  $EventTarget.removeEventListener(window, event.type, listener, useCapture);
+}, useCapture);