Adding the following stylus metrics:

1. Number of “down” events generated by stylus/touch/mouse
2. Number of “down” events received by clamshell vs touchview

BUG=630070

Review-Url: https://codereview.chromium.org/2270173002
Cr-Commit-Position: refs/heads/master@{#414304}

ash/BUILD.gn

@@ -140,6 +140,8 @@ component("ash") {
       "touch/touchscreen_util.h",
       "virtual_keyboard_controller.cc",
       "virtual_keyboard_controller.h",
+      "wm/stylus_metrics_recorder.cc",
+      "wm/stylus_metrics_recorder.h",
     ]
   }
 

ash/ash.gyp

@@ -776,6 +776,8 @@
       'wm/session_state_animator_impl.h',
       'wm/stacking_controller.cc',
       'wm/stacking_controller.h',
+      'wm/stylus_metrics_recorder.cc',
+      'wm/stylus_metrics_recorder.h',
       'wm/system_background_controller.cc',
       'wm/system_background_controller.h',
       'wm/system_gesture_event_filter.cc',
@@ -1193,7 +1195,9 @@
             'touch/touchscreen_util.cc',
             'touch/touchscreen_util.h',
             'virtual_keyboard_controller.cc',
-            'virtual_keyboard_controller.h'
+            'virtual_keyboard_controller.h',
+            'wm/stylus_metrics_recorder.cc',
+            'wm/stylus_metrics_recorder.h'
           ],
         }],
       ],

ash/shell.cc

@@ -128,6 +128,7 @@
 #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"
@@ -552,6 +553,9 @@ 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.
@@ -640,9 +644,7 @@ Shell::~Shell() {
 
 #if defined(OS_CHROMEOS)
   touch_transformer_controller_.reset();
-#endif  // defined(OS_CHROMEOS)
-
-#if defined(OS_CHROMEOS)
+  stylus_metrics_recorder_.reset();
   audio_a11y_controller_.reset();
 #endif  // defined(OS_CHROMEOS)
 
@@ -864,6 +866,14 @@ 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.

ash/shell.h

@@ -120,6 +120,7 @@ struct ShellInitParams;
 class SlowAnimationEventFilter;
 class StatusAreaWidget;
 class StickyKeysController;
+class StylusMetricsRecorder;
 class SystemGestureEventFilter;
 class SystemModalContainerEventFilter;
 class SystemTray;
@@ -576,6 +577,7 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
 
   std::unique_ptr<ui::EventHandler> magnifier_key_scroll_handler_;
   std::unique_ptr<ui::EventHandler> speech_feedback_handler_;
+  std::unique_ptr<StylusMetricsRecorder> stylus_metrics_recorder_;
 #endif  // defined(OS_CHROMEOS)
 
   // |native_cursor_manager_| is owned by |cursor_manager_|, but we keep a

ash/wm/stylus_metrics_recorder.cc

+// Copyright 2016 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 "ash/wm/stylus_metrics_recorder.h"
+
+#include "ash/common/wm/maximize_mode/maximize_mode_controller.h"
+#include "ash/common/wm_shell.h"
+#include "ash/shell.h"
+#include "base/metrics/histogram.h"
+#include "ui/events/event.h"
+#include "ui/events/event_constants.h"
+#include "ui/events/event_utils.h"
+
+namespace ash {
+
+// Form factor of the down event. This enum is used to back an UMA histogram
+// and should be treated as append-only.
+enum DownEventFormFactor {
+  DOWN_EVENT_FORMFACTOR_CLAMSHELL = 0,
+  DOWN_EVENT_FORMFACTOR_TOUCHVIEW,
+  DOWN_EVENT_FORMFACTOR_COUNT
+};
+
+// Input type of the down event. This enum is used to back an UMA histogram
+// and should be treated as append-only.
+enum DownEventSource {
+  DOWN_EVENT_SOURCE_UNKNOWN = 0,
+  DOWN_EVENT_SOURCE_MOUSE,
+  DOWN_EVENT_SOURCE_STYLUS,
+  DOWN_EVENT_SOURCE_TOUCH,
+  DOWN_EVENT_SOURCE_COUNT
+};
+
+StylusMetricsRecorder::StylusMetricsRecorder() {}
+
+StylusMetricsRecorder::~StylusMetricsRecorder() {}
+
+void StylusMetricsRecorder::OnMouseEvent(ui::MouseEvent* event) {
+  if (event->type() != ui::ET_MOUSE_PRESSED)
+    return;
+  RecordUMA(event->pointer_details().pointer_type);
+}
+
+void StylusMetricsRecorder::OnTouchEvent(ui::TouchEvent* event) {
+  if (event->type() != ui::ET_TOUCH_PRESSED)
+    return;
+  RecordUMA(event->pointer_details().pointer_type);
+}
+
+void StylusMetricsRecorder::RecordUMA(ui::EventPointerType type) {
+  DownEventFormFactor form_factor = DOWN_EVENT_FORMFACTOR_CLAMSHELL;
+  if (WmShell::Get()
+          ->maximize_mode_controller()
+          ->IsMaximizeModeWindowManagerEnabled()) {
+    form_factor = DOWN_EVENT_FORMFACTOR_TOUCHVIEW;
+  }
+  UMA_HISTOGRAM_ENUMERATION("Event.DownEventCount.PerFormFactor", form_factor,
+                            DOWN_EVENT_FORMFACTOR_COUNT);
+
+  DownEventSource input_type = DOWN_EVENT_SOURCE_UNKNOWN;
+  switch (type) {
+    case ui::EventPointerType::POINTER_TYPE_UNKNOWN:
+      input_type = DOWN_EVENT_SOURCE_UNKNOWN;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_MOUSE:
+      input_type = DOWN_EVENT_SOURCE_MOUSE;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_PEN:
+      input_type = DOWN_EVENT_SOURCE_STYLUS;
+      break;
+    case ui::EventPointerType::POINTER_TYPE_TOUCH:
+      input_type = DOWN_EVENT_SOURCE_TOUCH;
+      break;
+  }
+
+  UMA_HISTOGRAM_ENUMERATION("Event.DownEventCount.PerInput", input_type,
+                            DOWN_EVENT_SOURCE_COUNT);
+}
+
+}  // namespace ash

ash/wm/stylus_metrics_recorder.h

+// Copyright 2016 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.
+
+#ifndef ASH_WM_STYLUS_METRICS_RECORDER_H_
+#define ASH_WM_STYLUS_METRICS_RECORDER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "ui/events/event_handler.h"
+
+namespace ash {
+
+// An event recorder that record stylus related metrics.
+class StylusMetricsRecorder : public ui::EventHandler {
+ public:
+  StylusMetricsRecorder();
+  ~StylusMetricsRecorder() override;
+
+ private:
+  // ui::EventHandler:
+  void OnMouseEvent(ui::MouseEvent* event) override;
+  void OnTouchEvent(ui::TouchEvent* event) override;
+
+  void RecordUMA(ui::EventPointerType type);
+
+  DISALLOW_COPY_AND_ASSIGN(StylusMetricsRecorder);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_STYLUS_METRICS_RECORDER_H_

tools/metrics/histograms/histograms.xml

@@ -12759,6 +12759,20 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.DownEventCount.PerFormFactor" enum="DownEventFormFactor">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Counts the number of down events generated by clamshell/touchview.
+  </summary>
+</histogram>
+
+<histogram name="Event.DownEventCount.PerInput" enum="DownEventSource">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Counts the number of down events generated by Mouse/Touch/Stylus.
+  </summary>
+</histogram>
+
 <histogram name="Event.DragDrop.Cancel" enum="DragDropEventSource">
   <owner>mfomitchev@chromium.org</owner>
   <summary>
@@ -74081,6 +74095,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="GET_NON_CACHABLE"/>
 </enum>
 
+<enum name="DownEventFormFactor" type="int">
+  <int value="0" label="Clamshell"/>
+  <int value="1" label="Touchview"/>
+</enum>
+
+<enum name="DownEventSource" type="int">
+  <int value="0" label="Unknown"/>
+  <int value="1" label="Mouse"/>
+  <int value="2" label="Stylus"/>
+  <int value="3" label="Touch"/>
+</enum>
+
 <enum name="DownloadContentDisposition" type="int">
   <int value="0" label="Content-Disposition header present"/>
   <int value="1" label="Valid"/>