[views] Changes iteration over |children_| to use range-based for loops (reland)

ui/views/view.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_VIEWS_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 66 matching lines @@
 class ViewObserver;
 class Widget;
 class WordLookupClient;
 
 namespace internal {
 class PreEventDispatchHandler;
 class PostEventDispatchHandler;
 class RootView;
 }
 
+namespace {
+class ScopedChildrenLock;
+}

[sadrul, 2016/12/24 00:13:11]

Oh, missed this, sorry. This should not be in anonymous namespace. This can move
into the internal namespace.

+
 /////////////////////////////////////////////////////////////////////////////
 //
 // View class
 //
 //   A View is a rectangle within the views View hierarchy. It is the base
 //   class for all Views.
 //
 //   A View is a container of other Views (there is no such thing as a Leaf
 //   View - makes code simpler, reduces type conversion headaches, design
 //   mistakes etc)
@@ skipping 1126 matching lines @@
   // decide which object should be used to obtain the children, but this
   // function makes the decision explicit.
   std::string DoPrintViewGraph(bool first, View* view_with_children);
 #endif
 
  private:
   friend class internal::PreEventDispatchHandler;
   friend class internal::PostEventDispatchHandler;
   friend class internal::RootView;
   friend class FocusManager;
+  friend class ScopedChildrenLock;
   friend class ViewLayerTest;
   friend class Widget;
 
   // Painting  -----------------------------------------------------------------
 
   enum SchedulePaintType {
     // Indicates the size is the same (only the origin changed).
     SCHEDULE_PAINT_SIZE_SAME,
 
     // Indicates the size changed (and possibly the origin).
@@ skipping 216 matching lines @@
   int group_;
 
   // Tree operations -----------------------------------------------------------
 
   // This view's parent.
   View* parent_;
 
   // This view's children.
   Views children_;
 
+#if DCHECK_IS_ON()
+  // True while iterating over |children_|. Used to detect and DCHECK when
+  // |children_| is mutated during iteration.
+  mutable bool iterating_;
+#endif
+
   // Size and disposition ------------------------------------------------------
 
   // This View's bounds in the parent coordinate system.
   gfx::Rect bounds_;
 
   // Whether this view is visible.
   bool visible_;
 
   // Whether this view is enabled.
   bool enabled_;
@@ skipping 104 matching lines @@
   // Observers -------------------------------------------------------------
 
   base::ObserverList<ViewObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_