Only use ARC++ work-around when the focused node root is not desktop.

This fixes a bug where STS could read information behind the lock screen.

Bug: 831418
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I25e79e777042dc3c0b2e40a8cbf5fdb6f6ee42cb
Reviewed-on: https://chromium-review.googlesource.com/1010823
Commit-Queue: Katie Dektar <katie@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550805}

chrome/browser/resources/chromeos/select_to_speak/select_to_speak.js

@@ -298,8 +298,13 @@ SelectToSpeak.prototype = {
       // which is computed based on which window is the event handler for the
       // hit point, isn't the part of the tree that contains the actual
       // content. In such cases, use focus to get the root.
-      if (!findAllMatching(root, rect, nodes) && focusedNode)
+      // TODO(katie): Determine if this work-around needs to be ARC++ only. If
+      // so, look for classname exoshell on the root or root parent to confirm
+      // that a node is in ARC++.
+      if (!findAllMatching(root, rect, nodes) && focusedNode &&
+          focusedNode.root.role != RoleType.DESKTOP) {
         findAllMatching(focusedNode.root, rect, nodes);
+      }
       this.startSpeechQueue_(nodes);
       this.recordStartEvent_(START_SPEECH_METHOD_MOUSE);
     }.bind(this));