MacViews: Don't set window's alpha to 0 if window is already visible.

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 b0ab01429cdce334feb89a25766c3dd61b38532a..16656fd5be0625a0700ef268b05233a8c81607f6 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -552,7 +552,10 @@ void BridgedNativeWidget::SetVisibilityState(WindowVisibilityState new_state) {
   //  - A parent changing visibility updates child window visibility.
   //    * But only when changed via this function - ignore changes via the
   //      NSWindow API, or changes propagating out from here.
-  wants_to_be_visible_ = new_state != HIDE_WINDOW;
+  const bool wants_to_be_visible = new_state != HIDE_WINDOW;
+  if (wants_to_be_visible == wants_to_be_visible_)
+    return;
+  wants_to_be_visible_ = wants_to_be_visible;
 
   if (new_state == HIDE_WINDOW) {
     [window_ orderOut:nil];