Do not consider rootWebArea nodes not parented by webView to be roots

In ARC++, particularly notifications, we want to allow navigation to
continue outside of the root.

notifications (each of which is within its own root).

Test: alt+shift+n; search+right. Verify trversal through all
Bug: 778070
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Id1493a7bfd7d3757328d5f0e4067d885ab85bd18
Reviewed-on: https://chromium-review.googlesource.com/806756Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521779}

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_predicate.js

@@ -324,7 +324,9 @@ AutomationPredicate.root = function(node) {
         // to be crossed when performing traversals up the ancestry chain.
         return false;
       }
-      return !node.parent || node.parent.root.role == Role.DESKTOP;
+      return !node.parent ||
+          (node.parent.root.role == Role.DESKTOP &&
+           node.parent.role == Role.WEB_VIEW);
     default:
       return false;
   }