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

ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc

Index: ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc b/ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc
index 8a56b8de9689f8132adc9f2190b3154f4dced4b0..ab79efa8f6c7c26d160953f48a1436f96773beee 100644
--- a/ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc
+++ b/ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.cc
@@ -9,6 +9,7 @@
 #include "base/event_types.h"
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram_macros.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/window.h"
@@ -610,6 +611,10 @@ void DesktopDragDropClientAuraX11::OnXdndDrop(
         event.set_flags(XGetModifiers());
       }
 
+      if (!IsDragDropInProgress()) {
+        UMA_HISTOGRAM_COUNTS("DragDrop.ExternalOriginDrop", 1);
+      }
+
       drag_operation = delegate->OnPerformDrop(event);
     }
 
@@ -646,6 +651,9 @@ int DesktopDragDropClientAuraX11::StartDragAndDrop(
     const gfx::Point& root_location,
     int operation,
     ui::DragDropTypes::DragEventSource source) {
+  UMA_HISTOGRAM_ENUMERATION("DragDrop.Start", source,
+                            ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+
   source_current_window_ = None;
   DCHECK(!g_current_drag_drop_client);
   g_current_drag_drop_client = this;
@@ -698,6 +706,14 @@ int DesktopDragDropClientAuraX11::StartDragAndDrop(
       source_window,
       cursor_manager_->GetInitializedCursor(ui::kCursorGrabbing));
 
+  if (negotiated_operation_ == ui::DragDropTypes::DRAG_NONE) {

[pkotwicz, 2015/01/22 19:00:30]

Can you please change the "alive if statement" to be the following:

if (!alive) {
  UMA_HISTOGRAM_ENUMERATION("DragDrop.Cancel", source,
ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
  return ui::DragDropTypes::DRAG_NONE;
}

if (negotiated_operation_ == ui::DragDropTypes::DRAG_NONE) {
  ...
} else {
  ...
}

drag_widget_.reset()

source_provider_ = NULL;
...

Can you move the UMA histograms after the "alive if". If !|alive|, accessing
|negotiated_operation_| will cause a crash. |alive| is false when the drag and
drop source browser window is closed during the drag and drop operation. An evil
browser extension can close the browser window during a drag and drop operation.
I think that this case is covered by BookmarkBarViewTest22.*

[caelyn, 2015/01/22 21:13:08]

I moved if (negotiated_operation == ...) section inside the if alive section,
and added an else to record a cancel and return DRAG_NONE

+    UMA_HISTOGRAM_ENUMERATION("DragDrop.Cancel", source,
+                              ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("DragDrop.Drop", source,
+                              ui::DragDropTypes::DRAG_EVENT_SOURCE_COUNT);
+  }
+
   if (alive) {
     drag_widget_.reset();