views: Some more layer change, and add/update some tests for layers.

views/controls/native_control_gtk.cc

Index: views/controls/native_control_gtk.cc
diff --git a/views/controls/native_control_gtk.cc b/views/controls/native_control_gtk.cc
index 965d34738c194215329ca08a25fb57a8b23bc847..a798bc600ac78ac42d515591c9ca5ea6dd5d61cd 100644
--- a/views/controls/native_control_gtk.cc
+++ b/views/controls/native_control_gtk.cc
@@ -172,15 +172,7 @@ void NativeControlGtk::ViewHierarchyChanged(bool is_add, View* parent,
 }
 
 void NativeControlGtk::VisibilityChanged(View* starting_from, bool is_visible) {
-  if (!is_visible) {
-    if (native_view()) {
-      // We destroy the child widget when we become invisible because of the
-      // performance cost of maintaining widgets that aren't currently needed.
-      Detach();
-      // Make sure that Detach destroyed the widget.
-      DCHECK(!native_view());
-    }
-  } else if (!native_view()) {
+  if (!native_view()) {
     if (GetWidget())
       CreateNativeControl();
   } else {