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 49c20e9095ddc84cb818dedecaff2cc945d4e53d..25699e500dccb2fc9600753792c9369fba65f860 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_macros.h"
 #include "base/tracked_objects.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/drag_source_win.h"
@@ -45,6 +46,9 @@ int DesktopDragDropClientWin::StartDragAndDrop(
 
   DWORD effect;
 
+  UMA_HISTOGRAM_ENUMERATION("Event.DragDrop.Start", source,
+                            ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+
   // Use task stopwatch to exclude the drag-drop time current task, if any.
   tracked_objects::TaskStopwatch stopwatch;
   stopwatch.Start();
@@ -59,7 +63,17 @@ int DesktopDragDropClientWin::StartDragAndDrop(
   if (result != DRAGDROP_S_DROP)
     effect = DROPEFFECT_NONE;
 
-  return ui::DragDropTypes::DropEffectToDragOperation(effect);
+  int drag_operation = ui::DragDropTypes::DropEffectToDragOperation(effect);
+
+  if (drag_operation == ui::DragDropTypes::DRAG_NONE) {
+    UMA_HISTOGRAM_ENUMERATION("Event.DragDrop.Cancel", source,
+                              ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("Event.DragDrop.Drop", source,
+                              ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+  }
+
+  return drag_operation;
 }
 
 void DesktopDragDropClientWin::DragUpdate(aura::Window* target,