Adding UMA stats for dragdrop events for both touch and mouse.

ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc

Index: ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc
diff --git a/ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc b/ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc
index d135a8977a06f88374a331a3990b12e4922d0f54..3d1f89b955be990c63475feacf6e55c3ec6cb24c 100644
--- a/ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc
+++ b/ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc
@@ -4,6 +4,7 @@
 
 #include "ui/views/widget/desktop_aura/desktop_drag_drop_client_win.h"
 
+#include "base/metrics/histogram.h"
 #include "base/tracked_objects.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/drag_source_win.h"
@@ -38,6 +39,12 @@ int DesktopDragDropClientWin::StartDragAndDrop(
   drag_source_ = new ui::DragSourceWin;
   DWORD effect;
 
+  if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_TOUCH) {
+    UMA_HISTOGRAM_COUNTS("DragDrop.Touch.Start", 1);
+  } else if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_MOUSE) {
+    UMA_HISTOGRAM_COUNTS("DragDrop.Mouse.Start", 1);
+  }
+
   // Use task stopwatch to exclude the drag-drop time current task, if any.
   tracked_objects::TaskStopwatch stopwatch;
   stopwatch.Start();
@@ -51,7 +58,18 @@ int DesktopDragDropClientWin::StartDragAndDrop(
   if (result != DRAGDROP_S_DROP)
     effect = DROPEFFECT_NONE;
 
-  return ui::DragDropTypes::DropEffectToDragOperation(effect);
+  ui::DragDropTypes::DragOperation drag_operation =
+      ui::DragDropTypes::DropEffectToDragOperation(effect);
+
+  if (drag_operation != ui::DragDropTypes::DRAG_NONE) {

[mfomitchev, 2015/01/08 23:30:59]

If the operation is not NONE, shouldn't we log a cancel?

[caelyn, 2015/01/12 22:43:10]

If the drag_operation is DRAG_NONE, then we know the either things were
cancelled, or the object was dropped somewhere with no on drop functionality.

If the drag_operation is *not* DRAG_NONE, then we know some kind of drop
operation successfully completed.

At least, that is my understanding of this code. I could be wrong.

I have started tracking the 'drag_operation == DRAG_NONE' case as a cancel.

+    if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_TOUCH) {
+      UMA_HISTOGRAM_COUNTS("DragDrop.Touch.Drop", 1);
+    } else if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_MOUSE) {
+      UMA_HISTOGRAM_COUNTS("DragDrop.Mouse.Drop", 1);
+    }
+  }
+
+  return drag_operation;
 }
 
 void DesktopDragDropClientWin::DragUpdate(aura::Window* target,