Mac: Convince the WindowServer to update the print preview shadow on retina screens

ui/base/cocoa/constrained_window/constrained_window_animation.mm

Index: ui/base/cocoa/constrained_window/constrained_window_animation.mm
diff --git a/ui/base/cocoa/constrained_window/constrained_window_animation.mm b/ui/base/cocoa/constrained_window/constrained_window_animation.mm
index 3618a1b97825fc36365861ab3d3928d170cb3f2b..e467e0c85d4c95dedf81075250dfc1650a193336 100644
--- a/ui/base/cocoa/constrained_window/constrained_window_animation.mm
+++ b/ui/base/cocoa/constrained_window/constrained_window_animation.mm
@@ -223,6 +223,16 @@ void UpdateWindowShowHideAnimationState(NSWindow* window, CGFloat value) {
 
   if (progress >= 1.0) {
     [self setWindowStateForEnd];
+
+    // Starting in 10.10, the WindowServer forgets to draw the shadow on windows
+    // that animate in this way on retina screens. -[NSWindow invalidateShadow]
+    // doesn't fix it. Neither does toggling -setHasShadow:. But forcing an
+    // update to the window size, and then undoing it, seems to fix the problem.
+    // See http://crbug.com/436884.
+    // TODO(tapted): Find a better fix (this is horrible).
+    NSRect frame = [window_ frame];
+    [window_ setFrame:NSInsetRect(frame, 1, 1) display:NO animate:NO];
+    [window_ setFrame:frame display:NO animate:NO];

[erikchen, 2016/05/09 05:29:06]

uh. okay. I guess. In general I prefer moving away from private APIs, especially
when they cause problems.

[tapted, 2016/05/09 05:35:56]

I hear ya :). I think to resolve this we'd need to either drastically change or
remove the animations, and/or draw the shadow ourselves (maybe by extending the
size of the window slightly and giving the WebContents a parent layer).

Even using the "supported" animations from -[NSWindow animationBehaviour] might
not cope with the layer stuff.

     return;
   }
   [self setWindowStateForValue:[self currentValue]];