[VR Shell] Fix hidden elements being hit-testable.

chrome/browser/resources/vr_shell/vr_shell_ui.js

Index: chrome/browser/resources/vr_shell/vr_shell_ui.js
diff --git a/chrome/browser/resources/vr_shell/vr_shell_ui.js b/chrome/browser/resources/vr_shell/vr_shell_ui.js
index 2fd4a7a43d4b186dc18ed163e91a6d93d4779f01..bed2dcf932ee572a569d75cda5cd5ea3040f79b0 100644
--- a/chrome/browser/resources/vr_shell/vr_shell_ui.js
+++ b/chrome/browser/resources/vr_shell/vr_shell_ui.js
@@ -54,11 +54,12 @@ var vrShellUi = (function() {
       // Place an invisible but hittable plane behind the content quad, to keep
       // the reticle roughly planar with the content if near content.
       let backPlane = new api.UiElement(0, 0, 0, 0);
-      backPlane.setVisible(false);
+      backPlane.setVisible(true);

[cjgrant, 2017/02/24 14:25:23]

Why not remove setVisible() and setHitTestable() completely, as they are the
defaults?  The comment says "an invisible", and the first setter is
visibility(true). :)  The comment could also use a tweak.

[mthiesse, 2017/02/24 15:30:09]

Done.

       backPlane.setHitTestable(true);
       backPlane.setSize(1000, 1000);
       backPlane.setTranslation(0, 0, -0.01);
       backPlane.setParentId(this.elementId);
+      backPlane.setFill(new api.Fill(api.FillType.None));
       ui.addElement(backPlane);
 
       this.updateState();