MacViews: Attach child windows when parent is on the screen.

ui/views/cocoa/views_nswindow_delegate.mm

Index: ui/views/cocoa/views_nswindow_delegate.mm
diff --git a/ui/views/cocoa/views_nswindow_delegate.mm b/ui/views/cocoa/views_nswindow_delegate.mm
index 75346a6a8076dadb929abc2f858e5a2cf57e6892..5579dd338fbca95e6c96840f2525eabea5e09984 100644
--- a/ui/views/cocoa/views_nswindow_delegate.mm
+++ b/ui/views/cocoa/views_nswindow_delegate.mm
@@ -35,10 +35,6 @@
   [parent_->ns_window() resetCursorRects];
 }
 
-- (void)onWindowOrderWillChange:(NSWindowOrderingMode)orderingMode {
-  parent_->OnVisibilityChangedTo(orderingMode != NSWindowOut);

[tapted, 2016/06/17 04:33:05]

So you're correct that this shouldn't be calling OnVisibilityChangedTo(true) --
if [NSWindow visible] is still reporting NO, then that's likely to screw up the
child window relationships. But this was added  to ensure we have a valid
`paint` before the window becomes visible -- we still need that hook. i.e. it's
still a bug that windows come out of minimize "blank", and that windows appear
on screen first with blank background before the content appears. We need to
generalize the stuff that's done for modal sheets in void
BridgedNativeWidget::ShowAsModalSheet() -- the code there ensures the window
contents are available. We need to do the same for windows first appearing on
screen, and for windows coming out of minimize. Do you want to give this a go?

[kirr, 2016/06/20 16:15:54]

Sorry for delay.
I've checked blank window blinking one more time.

First thing is that now there is a blinking. So removing this line should not
change anything to worse.

Also I've tried to fix it as you say, by showing a layer and waiting for a frame
and then change window visibility.
Here is a draft
https://gist.github.com/anonymous/1607657661087e0ca73e0352495c47cf

It's working. But I think that it's better to fix it as render_widget_host_view
does. It leaves the CALayer visible and suspend compositor. Maybe some aura code
expect that native widget visibility is equal to layer visibility. I think it's
better to try and see if tests fails.

So, can we commit this CL as it is (maybe with test)? And fix blinking in
another one.

-}
-
 - (void)onWindowOrderChanged:(NSNotification*)notification {
   parent_->OnVisibilityChanged();
 }