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..8597a8e3e75d792e4c94b771781642575ac96414 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::TimeTicks::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() {

[jdduke (slow), 2015/02/09 16:10:56]

Hmm, on second thought, if this will need to change for when we unify, I'm fine
with leaving it out. I guess I'm also curious what the duration of the selection
means, and how actionable it is... What does the duration of the selection tell
us?

[mfomitchev, 2015/02/09 17:09:32]

My hope is that getting this into M42 will help us understand if the new
selection granularity strategy (which I plan to get into M43) improves the UX.

Generally we want the duration to go down and the success rate to go up. Now,
this is more tricky when duration is the only thing we are logging, because the
avg duration may decrease b/c of accidental selections. Still, I think having
some information here would be useful. E.g. if we implement nothing to affect
the number of accidental selections, while implementing a new selection
granularity strategy, and the duration goes down - we can hypothesize that with
a high degree of likelihood that is because the new selection strategy is
working well. And vice versa.

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