UMA stats for stylus usage

chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc
index 66fc3b85a2e3f5291e5506d1d33a1e03db5ea378..ab55cf5bbe5fee7b23f9c852d57385575223c152 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.cc
@@ -877,9 +877,16 @@ void ChromeLauncherControllerImpl::OnShelfCreated(ash::WmShelf* shelf) {
 
   if (ash::ShelfWidget::ShelfAlignmentAllowed())
     shelf->SetAlignment(ash::launcher::GetShelfAlignmentPref(prefs, display));
+#if defined(OS_CHROMEOS)
+  stylus_metrics_recorder_.reset(new chromeos::StylusMetricsRecorder());

[sky, 2016/09/13 00:03:25]

Use MakeUnique (search for examples in code if not familiar with it).

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:15]

Done.

+#endif
 }
 
-void ChromeLauncherControllerImpl::OnShelfDestroyed(ash::WmShelf* shelf) {}
+void ChromeLauncherControllerImpl::OnShelfDestroyed(ash::WmShelf* shelf) {
+#if defined(OS_CHROMEOS)

[sky, 2016/09/13 00:03:25]

Please document why this needs to be explicitly destroyed.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:15]

Done.

+  stylus_metrics_recorder_.reset();
+#endif
+}
 
 void ChromeLauncherControllerImpl::OnShelfAlignmentChanged(
     ash::WmShelf* shelf) {