linux_aura: Close window when the OS requests it.

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

Index: ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
index 4e6c1c4e46da570505d5db71e9ed736515f10ab6..26828e00f96793cc1cb32b9069fafad76352648e 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
@@ -178,6 +178,8 @@ DesktopNativeWidgetAura::~DesktopNativeWidgetAura() {
     CloseNow();
 
   stacking_client_.reset();  // Uses root_window_ at destruction.
+
+  root_window_->RemoveRootWindowObserver(this);
   root_window_.reset();  // Uses input_method_event_filter_ at destruction.
   input_method_event_filter_.reset();
 }
@@ -235,6 +237,8 @@ void DesktopNativeWidgetAura::InitNativeWidget(
                                     this, params.bounds);
   root_window_.reset(
       desktop_root_window_host_->Init(window_, params));
+  root_window_->AddRootWindowObserver(this);
+
   stacking_client_.reset(
       new DesktopNativeWidgetAuraStackingClient(root_window_.get()));
   drop_helper_.reset(new DropHelper(
@@ -842,4 +846,12 @@ int DesktopNativeWidgetAura::OnPerformDrop(const ui::DropTargetEvent& event) {
       last_drop_operation_);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// DesktopNativeWidgetAura, aura::RootWindowObserver implementation:
+
+void DesktopNativeWidgetAura::OnRootWindowHostCloseRequested(
+    const aura::RootWindow* root) {
+  Close();
+}
+
 }  // namespace views