UMA stats for stylus usage

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 8c92ec3d2bbe7a9d751d20d0a4dbb2fce8be4a3b..91aff2ab400d546f964d3f6b7fe1f1d3530bf3f5 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -129,7 +129,6 @@
 #include "ash/system/chromeos/power/video_activity_notifier.h"
 #include "ash/touch/touch_transformer_controller.h"
 #include "ash/virtual_keyboard_controller.h"
-#include "ash/wm/stylus_metrics_recorder.h"
 #include "base/bind_helpers.h"
 #include "base/sys_info.h"
 #include "chromeos/audio/audio_a11y_controller.h"
@@ -468,9 +467,6 @@ Shell::~Shell() {
   RemovePostTargetHandler(toplevel_window_event_handler_.get());
   RemovePreTargetHandler(system_gesture_filter_.get());
   RemovePreTargetHandler(mouse_cursor_filter_.get());
-#if defined(OS_CHROMEOS)
-  RemovePreTargetHandler(stylus_metrics_recorder_.get());
-#endif
   RemovePreTargetHandler(modality_filter_.get());
 
   // TooltipController is deleted with the Shell so removing its references.
@@ -559,7 +555,6 @@ Shell::~Shell() {
 
 #if defined(OS_CHROMEOS)
   touch_transformer_controller_.reset();
-  stylus_metrics_recorder_.reset();
   audio_a11y_controller_.reset();
   laser_pointer_controller_.reset();
   partial_magnification_controller_.reset();
@@ -772,14 +767,6 @@ void Shell::Init(const ShellInitParams& init_params) {
   mouse_cursor_filter_.reset(new MouseCursorEventFilter());
   PrependPreTargetHandler(mouse_cursor_filter_.get());
 
-#if defined(OS_CHROMEOS)
-  // |stylus_metrics_recorder| records stylus metrics for certain events.
-  // It does not handle/consume any events, so prepend it as a pre-target hander
-  // before events are consumed elsewhere.
-  stylus_metrics_recorder_.reset(new StylusMetricsRecorder());
-  PrependPreTargetHandler(stylus_metrics_recorder_.get());
-#endif
-
   // Create Controllers that may need root window.
   // TODO(oshima): Move as many controllers before creating
   // RootWindowController as possible.