MacViews: Allow views::Widgets to be parented off NSWindows

ui/views/widget/native_widget_mac.mm

 // 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 "ui/views/widget/native_widget_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 563 matching lines @@
   }
   return NULL;  // Not created by NativeWidgetMac.
 }
 
 // static
 NativeWidgetPrivate* NativeWidgetPrivate::GetTopLevelNativeWidget(
     gfx::NativeView native_view) {
   BridgedNativeWidget* bridge =
       NativeWidgetMac::GetBridgeForNativeWindow([native_view window]);
   if (!bridge)
-    return NULL;
+    return nullptr;
 
-  for (BridgedNativeWidget* parent;
-       (parent = bridge->parent());
-       bridge = parent) {
-  }
-  return bridge->native_widget_mac();
+  NativeWidgetPrivate* ancestor =
+      bridge->parent() ? GetTopLevelNativeWidget(
+                             [bridge->parent()->GetNSWindow() contentView])
+                       : nullptr;
+  return ancestor ? ancestor : bridge->native_widget_mac();
 }
 
 // static
 void NativeWidgetPrivate::GetAllChildWidgets(gfx::NativeView native_view,
                                              Widget::Widgets* children) {
   BridgedNativeWidget* bridge =
       NativeWidgetMac::GetBridgeForNativeWindow([native_view window]);
   if (!bridge)
     return;
 
@@ skipping 32 matching lines @@
 }
 
 // static
 gfx::FontList NativeWidgetPrivate::GetWindowTitleFontList() {
   NOTIMPLEMENTED();
   return gfx::FontList();
 }
 
 }  // namespace internal
 }  // namespace views