Enable touch-initiated drag-drop work on Windows

ui/base/dragdrop/drag_source_win.cc

 // Copyright (c) 2011 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/base/dragdrop/drag_source_win.h"
 
 namespace ui {
 
-DragSourceWin::DragSourceWin() : cancel_drag_(false) {
+DragSourceWin::DragSourceWin()
+    : cancel_drag_(false),
+      event_source_(DragDropTypes::DRAG_EVENT_SOURCE_MOUSE) {
+}
+
+DragSourceWin::DragSourceWin(DragDropTypes::DragEventSource event_source)
+    : cancel_drag_(false),
+      event_source_(event_source) {
 }
 
 HRESULT DragSourceWin::QueryContinueDrag(BOOL escape_pressed, DWORD key_state) {
   if (cancel_drag_)
     return DRAGDROP_S_CANCEL;
 
   if (escape_pressed) {
     OnDragSourceCancel();
     return DRAGDROP_S_CANCEL;
   }
 
-  if (!(key_state & MK_LBUTTON)) {
+  // On Windows, the touch-initiated drag-drop is driven by mouse right down
+  // event programmatically.
+  if ((event_source_ == DragDropTypes::DRAG_EVENT_SOURCE_MOUSE &&
+      !(key_state & MK_LBUTTON)) ||
+      (event_source_ == DragDropTypes::DRAG_EVENT_SOURCE_TOUCH &&
+      !(key_state && MK_RBUTTON))) {
     OnDragSourceDrop();
     return DRAGDROP_S_DROP;
   }
 
   OnDragSourceMove();
   return S_OK;
 }
 
 HRESULT DragSourceWin::GiveFeedback(DWORD effect) {
   return DRAGDROP_S_USEDEFAULTCURSORS;
@@ skipping 14 matching lines @@
   base::RefCountedThreadSafe<DragSourceWin>::AddRef();
   return 0;
 }
 
 ULONG DragSourceWin::Release() {
   base::RefCountedThreadSafe<DragSourceWin>::Release();
   return 0;
 }
 
 }  // namespace ui