MacViews: Implement CloseNow() as just -[NSWindow close].

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index 8e47513350dc150013b5a19023ea9e969f42d8e1..64310109fb4bc60b134e91c702c3856b6e0889f1 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -353,42 +353,15 @@ BridgedNativeWidget::BridgedNativeWidget(NativeWidgetMac* parent)
 }
 
 BridgedNativeWidget::~BridgedNativeWidget() {
-  bool close_window = false;
-  if ([window_ delegate]) {
-    // If the delegate is still set on a modal dialog, it means it was not
-    // closed via [NSApplication endSheet:]. This is probably OK if the widget
-    // was never shown. But Cocoa ignores close() calls on open sheets. Calling
-    // endSheet: here would work, but it messes up assumptions elsewhere. E.g.
-    // DialogClientView assumes its delegate is alive when closing, which isn't
-    // true after endSheet: synchronously calls OnNativeWidgetDestroyed().
-    // So ban it. Modal dialogs should be closed via Widget::Close().
-    DCHECK(!native_widget_mac_->IsWindowModalSheet());
-
-    // If the delegate is still set, it means OnWindowWillClose() has not been
-    // called and the window is still open. Usually, -[NSWindow close] would
-    // synchronously call OnWindowWillClose() which removes the delegate and
-    // notifies NativeWidgetMac, which then calls this with a nil delegate.
-    // For other teardown flows (e.g. Widget::WIDGET_OWNS_NATIVE_WIDGET or
-    // Widget::CloseNow()) the delegate must first be cleared to avoid AppKit
-    // calling back into the bridge. This means OnWindowWillClose() needs to be
-    // invoked manually, which is done below.
-    // Note that if the window has children it can't be closed until the
-    // children are gone, but removing child windows calls into AppKit for the
-    // parent window, so the delegate must be cleared first.
-    [window_ setDelegate:nil];
-    close_window = true;
-  }
+  // The delegate should be cleared already. Note this enforces the precondition
+  // that the hosted NSWindow is closed before the destructor is called.

[karandeepb, 2016/10/18 10:00:29]

Technically, the window hasn't closed yet right? We are still "inside" [NSWindow
close] and the delegate's windowWillClose method. Maybe this can be clarified
better. 

[tapted, 2016/10/19 06:20:25]

Done.

+  DCHECK(![window_ delegate]);
 
   RemoveOrDestroyChildren();
   DCHECK(child_windows_.empty());
   SetFocusManager(nullptr);
   SetRootView(nullptr);
   DestroyCompositor();
-
-  if (close_window) {
-    OnWindowWillClose();
-    [window_ close];
-  }
 }
 
 void BridgedNativeWidget::Init(base::scoped_nsobject<NSWindow> window,
@@ -706,6 +679,8 @@ void BridgedNativeWidget::SetCursor(NSCursor* cursor) {
 }
 
 void BridgedNativeWidget::OnWindowWillClose() {
+  native_widget_mac_->GetWidget()->OnNativeWidgetDestroying();
+
   // Ensure BridgedNativeWidget does not have capture, otherwise
   // OnMouseCaptureLost() may reference a deleted |native_widget_mac_| when
   // called via ~CocoaMouseCapture() upon the destruction of |mouse_capture_|.
@@ -719,10 +694,9 @@ void BridgedNativeWidget::OnWindowWillClose() {
     parent_ = nullptr;
   }
   [[NSNotificationCenter defaultCenter] removeObserver:window_delegate_];
-  // Note this also clears the NSWindow delegate, after informing Widget
-  // delegates about the closure. NativeWidgetMac then deletes |this| before
-  // returning.
-  native_widget_mac_->OnWindowWillClose();
+  [window_ setDelegate:nil];
+  native_widget_mac_->OnWindowDestroyed();
+  // Note: |this| is deleted here.
 }
 
 void BridgedNativeWidget::OnFullscreenTransitionStart(