Adds code to isolate use-after-free in Views

ui/views/view.cc

 // 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.
 
 #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
 
 #include "ui/views/view.h"
 
 #include <algorithm>
 #include <cmath>
@@ skipping 145 matching lines @@
   ViewStorage::GetInstance()->ViewRemoved(this);
 
   {
     internal::ScopedChildrenLock lock(this);
     for (auto* child : children_) {
       child->parent_ = NULL;
       if (!child->owned_by_client_)
         delete child;
     }
   }
+
+  for (ViewObserver& observer : observers_)
+    observer.OnViewIsDeleting(this);
 }
 
 // Tree operations -------------------------------------------------------------
 
 const Widget* View::GetWidget() const {
   // The root view holds a reference to this view hierarchy's Widget.
   return parent_ ? parent_->GetWidget() : NULL;
 }
 
 Widget* View::GetWidget() {
@@ skipping 2386 matching lines @@
   // Message the RootView to do the drag and drop. That way if we're removed
   // the RootView can detect it and avoid calling us back.
   gfx::Point widget_location(event.location());
   ConvertPointToWidget(this, &widget_location);
   widget->RunShellDrag(this, data, widget_location, drag_operations, source);
   // WARNING: we may have been deleted.
   return true;
 }
 
 }  // namespace views