Replaced is_null() with is_valid in SurfaceId and related classes.

services/ui/public/cpp/window.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/public/cpp/window.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <set>
@@ skipping 794 matching lines @@
 
   for (auto& observer : observers_)
     observer.OnWindowSharedPropertyChanged(this, name, old_value_ptr, value);
 }
 
 void Window::LocalSetSurfaceId(std::unique_ptr<SurfaceInfo> surface_info) {
   if (surface_info_) {
     const cc::SurfaceId& existing_surface_id = surface_info_->surface_id;
     cc::SurfaceId new_surface_id =
         surface_info ? surface_info->surface_id : cc::SurfaceId();
-    if (!existing_surface_id.is_null() &&
+    if (existing_surface_id.is_valid() &&
         existing_surface_id != new_surface_id) {
       // TODO(kylechar): Start return reference here?
     }
   }
   if (parent_ && parent_->surface_id_handler_) {
     parent_->surface_id_handler_->OnChildWindowSurfaceChanged(this,
                                                               &surface_info);
   }
   surface_info_ = std::move(surface_info);
 }
@@ skipping 137 matching lines @@
     notifier->NotifyWindowReordered();
 
   return true;
 }
 
 // static
 Window** Window::GetStackingTarget(Window* window) {
   return &window->stacking_target_;
 }
 }  // namespace ui