Fix SetShape (SetAlphaShape) to allow Null regions (+ tests).

chrome/browser/ui/views/apps/chrome_native_app_window_views.cc

Index: chrome/browser/ui/views/apps/chrome_native_app_window_views.cc
diff --git a/chrome/browser/ui/views/apps/chrome_native_app_window_views.cc b/chrome/browser/ui/views/apps/chrome_native_app_window_views.cc
index 3aecc9d01fdcf2f6a18b1cd4f2abaeca1a74a045..ed01f1127493ebd046daad67459dd2099c9ad8c1 100644
--- a/chrome/browser/ui/views/apps/chrome_native_app_window_views.cc
+++ b/chrome/browser/ui/views/apps/chrome_native_app_window_views.cc
@@ -661,12 +661,15 @@ void ChromeNativeAppWindowViews::UpdateShape(scoped_ptr<SkRegion> region) {
   aura::Window* native_window = widget()->GetNativeWindow();
   if (shape_) {
     widget()->SetShape(new SkRegion(*shape_));
+    native_window->layer()->SetAlphaShape(

[sky, 2014/08/11 15:26:37]

Why don't we implement this in the NativeWidget implementations?

[garykac, 2014/08/11 18:19:09]

I'm not sure - the original implementation was done by zork@ in
crrev.com/132343006.  This just re-adding the call now that the HiDPI issues
have been fixed.

zork: Do you have an answer for this?

[Zachary Kuznia, 2014/08/11 20:05:14]

The SetShape() function didn't exist on widget when I wrote the original patch. 
I don't think there's a reason the implementation couldn't be moved there now.

+        make_scoped_ptr(new SkRegion(*shape_)));
     if (!had_shape) {
       native_window->SetEventTargeter(scoped_ptr<ui::EventTargeter>(
           new ShapedAppWindowTargeter(native_window, this)));
     }
   } else {
     widget()->SetShape(NULL);
+    native_window->layer()->SetAlphaShape(scoped_ptr<SkRegion>());
     if (had_shape)
       native_window->SetEventTargeter(scoped_ptr<ui::EventTargeter>());
   }