Add passive and FOV-locked properties to UI elements.

chrome/browser/resources/vr_shell/vr_shell_ui_api.js

Index: chrome/browser/resources/vr_shell/vr_shell_ui_api.js
diff --git a/chrome/browser/resources/vr_shell/vr_shell_ui_api.js b/chrome/browser/resources/vr_shell/vr_shell_ui_api.js
index 085af162bf2600f6efc5969974201dd2424f0cea..e90757e343bf59fd9639aa12ffd0d8d8d2251774 100644
--- a/chrome/browser/resources/vr_shell/vr_shell_ui_api.js
+++ b/chrome/browser/resources/vr_shell/vr_shell_ui_api.js
@@ -163,6 +163,21 @@ var api = (function() {
     setVisible(visible) {
       this.visible = !!visible;
     }
+
+    /**
+     * Hit-testable implies that the reticle will hit the element, if visible.
+     */
+    setHitTestable(testable) {
+      this.hitTestable = !!testable;
+    }
+
+    /**
+     * Causes an element to be rendered relative to the field of view, rather
+     * than the scene.  Elements locked in this way should not have a parent.
+     */
+    setLockToFieldOfView(locked) {
+      this.lockToFov = !!locked;
+    }
   };
 
   /**