Add always-on-top property to app windows

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index 9261c7227d5f448a5f5083338c3b471e94275ff3..e7df069c18ee987aea95735addc1a72b52d13984 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -658,6 +658,10 @@ void Widget::SetAlwaysOnTop(bool on_top) {
   native_widget_->SetAlwaysOnTop(on_top);
 }
 
+bool Widget::IsAlwaysOnTop() const {
+  return native_widget_->IsAlwaysOnTop();

[sky, 2013/10/08 15:46:10]

Can we make widget cache the value of SetAlwaysOnTop so that we don't need to
always ask the underlying NativeWidget?

[tmdiep, 2013/10/09 02:15:04]

In Patch 4 I've retrieved and cached the value from the underlying NativeWidget
in SetAlwaysOnTop.  But did you mean just cache the argument passed to
SetAlwaysOnTop and remove IsAlwaysOnTop from all the views classes entirely?

Is there any case where the actual value would not match the argument? The only
reason I can think of is when the underlying platform doesn't implement an
always-on-top flag.

[sky, 2013/10/09 13:23:38]

Yes. I mean cache the value from InitParams and SetAlwaysOnTop. I'm assuming the
platform always honor it, if not you would not be able to detect it with my
approach. If you need to really know what the native platform is doing keep your
code.

[tmdiep, 2013/10/10 02:35:08]

I'm inclined to query IsAlwaysOnTop() from the native platform, as it just feels
like a more complete implementation. In the event that we do not to implement
this flag for a particular platform, I prefer the native widget returning false
over #ifdefs in Widget. But it's done for all platforms currently, so either
approach would work really.

+}
+
 void Widget::Maximize() {
   native_widget_->Maximize();
 }