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

ui/views/cocoa/widget_owner_nswindow_adapter.h

Index: ui/views/cocoa/widget_owner_nswindow_adapter.h
diff --git a/ui/views/cocoa/widget_owner_nswindow_adapter.h b/ui/views/cocoa/widget_owner_nswindow_adapter.h
new file mode 100644
index 0000000000000000000000000000000000000000..7356a6bb616a7338a3ad9558a8a1816142eda260
--- /dev/null
+++ b/ui/views/cocoa/widget_owner_nswindow_adapter.h
@@ -0,0 +1,47 @@
+// Copyright 2015 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_COCOA_WIDGET_OWNER_NSWINDOW_ADAPTER_H_
+#define UI_VIEWS_COCOA_WIDGET_OWNER_NSWINDOW_ADAPTER_H_
+
+#import "base/mac/scoped_nsobject.h"
+#import "ui/views/cocoa/bridged_native_widget_owner.h"
+
+@class NSView;
+@class WidgetOwnerNSWindowAdapterBridge;
+
+namespace views {
+
+// An adapter that allows a views::Widget to be owned by an NSWindow that is not
+// backed by another BridgedNativeWidget.
+class WidgetOwnerNSWindowAdapter : public BridgedNativeWidgetOwner {
+ public:
+  // Create an adapter that will own |child|, tying its lifetime with the
+  // NSWindow containing |anchor_view|. The object is self-deleting, via a call
+  // to RemoveChildWindow() made in child->OnWindowWillClose().
+  WidgetOwnerNSWindowAdapter(BridgedNativeWidget* child, NSView* anchor_view);
+
+  // Called when the owning window is closing.
+  void OnWindowWillClose();
+
+  // Overridden from BridgedNativeWidgetOwner:
+  NSWindow* GetNSWindow() override;
+  gfx::Vector2d ChildWindowOffset() override;
+  bool IsVisibleParent() override;
+  void RemoveChildWindow(BridgedNativeWidget* child) override;
+
+ private:
+  // Self-deleting.
+  ~WidgetOwnerNSWindowAdapter() override;
+
+  BridgedNativeWidget* child_;  // Weak. Owned by its NativeWidgetMac.
+  base::scoped_nsobject<NSView> anchor_view_;
+  base::scoped_nsobject<WidgetOwnerNSWindowAdapterBridge> observer_bridge_;
+
+  DISALLOW_COPY_AND_ASSIGN(WidgetOwnerNSWindowAdapter);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_COCOA_WIDGET_OWNER_NSWINDOW_ADAPTER_H_