Go back to the old method of doing file drop promises.

content/browser/web_contents/web_drag_source_mac.h

 // 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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/files/file_path.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 68 matching lines @@
 - (void)startDrag;
 
 // End the drag and clear the pasteboard; hook up to
 // -draggedImage:endedAt:operation:.
 - (void)endDragAt:(NSPoint)screenPoint
         operation:(NSDragOperation)operation;
 
 // Drag moved; hook up to -draggedImage:movedTo:.
 - (void)moveDragTo:(NSPoint)screenPoint;
 
+// Call to drag a promised file to the given path (should be called before
+// -endDragAt:...); hook up to -namesOfPromisedFilesDroppedAtDestination:.
+// Returns the file name (not including path) of the file deposited (or which
+// will be deposited).
+- (NSString*)dragPromisedFileTo:(NSString*)path;
+
 @end