Adding UMA logging to touch text selection

ui/touch_selection/touch_selection_controller.cc

Index: ui/touch_selection/touch_selection_controller.cc
diff --git a/ui/touch_selection/touch_selection_controller.cc b/ui/touch_selection/touch_selection_controller.cc
index d53f4095e05195aa24e52ff1f6ea2a45770a8632..16de0cb1019f938ebe930d82294a77a2ec080d00 100644
--- a/ui/touch_selection/touch_selection_controller.cc
+++ b/ui/touch_selection/touch_selection_controller.cc
@@ -6,6 +6,7 @@
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 
 namespace ui {
 namespace {
@@ -61,6 +62,8 @@ TouchSelectionController::TouchSelectionController(
 }
 
 TouchSelectionController::~TouchSelectionController() {
+  if (is_selection_active_)
+    LogSelectionEnd();
 }
 
 void TouchSelectionController::OnSelectionBoundsChanged(
@@ -385,7 +388,12 @@ void TouchSelectionController::ActivateSelection() {
   // an entirely new selection, notify the client but avoid sending an
   // intervening SELECTION_CLEARED update to avoid unnecessary state changes.
   if (!is_selection_active_ || response_pending_input_event_ == LONG_PRESS) {
+    if (is_selection_active_) {
+      // The active selection session finishes with the start of the new one.
+      LogSelectionEnd();
+    }
     is_selection_active_ = true;
+    selection_start_time_ = base::Time::Now();
     response_pending_input_event_ = INPUT_EVENT_TYPE_NONE;
     client_->OnSelectionEvent(SELECTION_SHOWN, GetStartPosition());
   }
@@ -396,6 +404,7 @@ void TouchSelectionController::DeactivateSelection() {
     return;
   DCHECK(start_selection_handle_);
   DCHECK(end_selection_handle_);
+  LogSelectionEnd();
   start_selection_handle_->SetEnabled(false);
   end_selection_handle_->SetEnabled(false);
   is_selection_active_ = false;
@@ -442,4 +451,13 @@ TouchHandle::AnimationStyle TouchSelectionController::GetAnimationStyle(
              : TouchHandle::ANIMATION_NONE;
 }
 
+void TouchSelectionController::LogSelectionEnd() {
+  base::TimeDelta duration = base::Time::Now() - selection_start_time_;

[jdduke (slow), 2015/02/05 21:00:28]

Shouldn't we be using TimeTicks (CPU time), not Time (wallclock time)?

[mfomitchev, 2015/02/05 21:28:31]

Good point. Fixed.

+  UMA_HISTOGRAM_CUSTOM_TIMES("Event.TouchSelectionDuration",
+                             duration,
+                             base::TimeDelta::FromMilliseconds(1),
+                             base::TimeDelta::FromSeconds(60),
+                             50);
+}
+
 }  // namespace ui