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

ui/views/widget/desktop_aura/desktop_drag_drop_client_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #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"
 #include "ui/base/dragdrop/drop_target_event.h"
 #include "ui/base/dragdrop/os_exchange_data_provider_win.h"
 #include "ui/views/widget/desktop_aura/desktop_drop_target_win.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_win.h"
 
 namespace views {
 
@@ skipping 14 matching lines @@
     aura::Window* source_window,
     const gfx::Point& root_location,
     int operation,
     ui::DragDropTypes::DragEventSource source) {
   drag_drop_in_progress_ = true;
   drag_operation_ = operation;
 
   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();
   HRESULT result = DoDragDrop(
       ui::OSExchangeDataProviderWin::GetIDataObject(data), drag_source_.get(),
       ui::DragDropTypes::DragOperationToDropEffect(operation), &effect);
   stopwatch.Stop();
 
   drag_drop_in_progress_ = false;
 
   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,
                                           const ui::LocatedEvent& event) {
 }
 
 void DesktopDragDropClientWin::Drop(aura::Window* target,
                                     const ui::LocatedEvent& event) {
 }
 
 void DesktopDragDropClientWin::DragCancel() {
   drag_source_->CancelDrag();
   drag_operation_ = 0;
 }
 
 bool DesktopDragDropClientWin::IsDragDropInProgress() {
   return drag_drop_in_progress_;
 }
 
 void DesktopDragDropClientWin::OnNativeWidgetDestroying(HWND window) {
   if (drop_target_.get()) {
     RevokeDragDrop(window);
     drop_target_ = NULL;
   }
 }
 
 }  // namespace views