VR: Route hover and click events to UI elements.

chrome/browser/android/vr_shell/ui_elements/ui_element.h

Index: chrome/browser/android/vr_shell/ui_elements/ui_element.h
diff --git a/chrome/browser/android/vr_shell/ui_elements/ui_element.h b/chrome/browser/android/vr_shell/ui_elements/ui_element.h
index 39acace488cbeb9f55fa27eaaf6b686440293de7..a4fbc171160f908bc10edb4ca3c494de792e5fd0 100644
--- a/chrome/browser/android/vr_shell/ui_elements/ui_element.h
+++ b/chrome/browser/android/vr_shell/ui_elements/ui_element.h
@@ -104,6 +104,11 @@ struct UiElement : public WorldRectangle {
 
   virtual void Initialize();
 
+  // Controller interaction methods.
+  virtual void OnMouseEnter();

[cjgrant, 2017/04/26 14:36:16]

I used Mouse by convention, but these could be OnHoverEnter/OnHoverLeave, or
something else.  Thoughts?

[mthiesse, 2017/04/26 16:09:49]

Hover enter/leave sound better to me.

+  virtual void OnMouseLeave();
+  virtual void OnClick();
+
   // Valid IDs are non-negative.
   int id = -1;