UMA stats for stylus usage

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

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 859 matching lines @@
 
 void ChromeLauncherControllerImpl::OnShelfCreated(ash::WmShelf* shelf) {
   PrefService* prefs = profile_->GetPrefs();
   const int64_t display = GetDisplayIDForShelf(shelf);
 
   shelf->SetAutoHideBehavior(
       ash::launcher::GetShelfAutoHideBehaviorPref(prefs, display));
 
   if (ash::ShelfWidget::ShelfAlignmentAllowed())
     shelf->SetAlignment(ash::launcher::GetShelfAlignmentPref(prefs, display));
+#if defined(OS_CHROMEOS)
+  stylus_metrics_recorder_ =
+      base::MakeUnique<chromeos::StylusMetricsRecorder>();
+#endif
 }
 
-void ChromeLauncherControllerImpl::OnShelfDestroyed(ash::WmShelf* shelf) {}
+void ChromeLauncherControllerImpl::OnShelfDestroyed(ash::WmShelf* shelf) {
+// To clean up stylus_metrics_recorder_ properly, a valid shell instance is
+// required. So explicityly delete it before the shell instance becomes invalid.

[xiyuan, 2016/09/16 20:07:54]

nit: wrong indent. Comment should use the same indent as code.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 22:34:25]

Done.

+#if defined(OS_CHROMEOS)

[xiyuan, 2016/09/16 20:07:54]

nit: move this above the comment to keep it closer to code.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 22:34:25]

Done.

+  stylus_metrics_recorder_.reset();
+#endif
+}
 
 void ChromeLauncherControllerImpl::OnShelfAlignmentChanged(
     ash::WmShelf* shelf) {
   ash::launcher::SetShelfAlignmentPref(
       profile_->GetPrefs(), GetDisplayIDForShelf(shelf), shelf->alignment());
 }
 
 void ChromeLauncherControllerImpl::OnShelfAutoHideBehaviorChanged(
     ash::WmShelf* shelf) {
   ash::launcher::SetShelfAutoHideBehaviorPref(profile_->GetPrefs(),
@@ skipping 818 matching lines @@
     if (index == -1)
       continue;
     ash::ShelfItem item = model_->items()[index];
     item.image = image;
     if (arc_deferred_launcher_)
       arc_deferred_launcher_->MaybeApplySpinningEffect(id, &item.image);
     model_->Set(index, item);
     // It's possible we're waiting on more than one item, so don't break.
   }
 }