Revert of Don't refcount tracking id -> slot id mapping.

ui/events/event.cc

Index: ui/events/event.cc
diff --git a/ui/events/event.cc b/ui/events/event.cc
index 1cd62e3d918793c39a6a6bfd9e62735ed4fc6488..d0966da00847a13bcfe64258596a445fa57bd0e4 100644
--- a/ui/events/event.cc
+++ b/ui/events/event.cc
@@ -526,17 +526,19 @@
       radius_y_(GetTouchRadiusY(native_event)),
       rotation_angle_(GetTouchAngle(native_event)),
       force_(GetTouchForce(native_event)),
-      should_remove_native_touch_id_mapping_(false) {
-  if (type() == ET_TOUCH_RELEASED || type() == ET_TOUCH_CANCELLED)
-    should_remove_native_touch_id_mapping_ = true;
+      may_cause_scrolling_(false) {
+  latency()->AddLatencyNumberWithTimestamp(
+      INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
+      0,
+      0,
+      base::TimeTicks::FromInternalValue(time_stamp().ToInternalValue()),
+      1);
 
   latency()->AddLatencyNumber(INPUT_EVENT_LATENCY_UI_COMPONENT, 0, 0);
-  FixRotationAngle();
-
-  latency()->AddLatencyNumberWithTimestamp(
-      INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT, 0, 0,
-      base::TimeTicks::FromInternalValue(time_stamp().ToInternalValue()), 1);
-  latency()->AddLatencyNumber(INPUT_EVENT_LATENCY_UI_COMPONENT, 0, 0);
+  fixRotationAngle();
+
+  if (type() == ET_TOUCH_PRESSED)
+    IncrementTouchIdRefCount(native_event);
 }
 
 TouchEvent::TouchEvent(EventType type,
@@ -550,7 +552,7 @@
       radius_y_(0.0f),
       rotation_angle_(0.0f),
       force_(0.0f),
-      should_remove_native_touch_id_mapping_(false) {
+      may_cause_scrolling_(false) {
   latency()->AddLatencyNumber(INPUT_EVENT_LATENCY_UI_COMPONENT, 0, 0);
 }
 
@@ -570,20 +572,17 @@
       radius_y_(radius_y),
       rotation_angle_(angle),
       force_(force),
-      should_remove_native_touch_id_mapping_(false) {
+      may_cause_scrolling_(false) {
   latency()->AddLatencyNumber(INPUT_EVENT_LATENCY_UI_COMPONENT, 0, 0);
-  FixRotationAngle();
+  fixRotationAngle();
 }
 
 TouchEvent::~TouchEvent() {
   // In ctor TouchEvent(native_event) we call GetTouchId() which in X11
   // platform setups the tracking_id to slot mapping. So in dtor here,
   // if this touch event is a release event, we clear the mapping accordingly.
-  if (should_remove_native_touch_id_mapping_) {
-    DCHECK(type() == ET_TOUCH_RELEASED || type() == ET_TOUCH_CANCELLED);
-    if (type() == ET_TOUCH_RELEASED || type() == ET_TOUCH_CANCELLED)
-      ClearTouchIdIfReleased(native_event());
-  }
+  if (HasNativeEvent())
+    ClearTouchIdIfReleased(native_event());
 }
 
 void TouchEvent::UpdateForRootTransform(
@@ -604,7 +603,7 @@
       static_cast<EventResult>(result() | ER_DISABLE_SYNC_HANDLING));
 }
 
-void TouchEvent::FixRotationAngle() {
+void TouchEvent::fixRotationAngle() {
   while (rotation_angle_ < 0)
     rotation_angle_ += 180;
   while (rotation_angle_ >= 180)