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

content/browser/web_contents/web_contents_view_mac.mm

 // 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 <Carbon/Carbon.h>
 
 #import "content/browser/web_contents/web_contents_view_mac.h"
 
 #include <string>
 
@@ skipping 494 matching lines @@
 
   // Might as well throw out this object now.
   dragSource_.reset();
 }
 
 // Called when a drag initiated in our view moves.
 - (void)draggedImage:(NSImage*)draggedImage movedTo:(NSPoint)screenPoint {
   [dragSource_ moveDragTo:screenPoint];
 }
 
+// Called when a file drag is dropped and the promised files need to be written.
+- (NSArray*)namesOfPromisedFilesDroppedAtDestination:(NSURL*)dropDest {
+  if (![dropDest isFileURL])
+    return nil;
+
+  NSString* fileName = [dragSource_ dragPromisedFileTo:[dropDest path]];
+  if (!fileName)
+    return nil;
+
+  return @[ fileName ];
+}
+
 // NSDraggingDestination methods
 
 - (NSDragOperation)draggingEntered:(id<NSDraggingInfo>)sender {
   return [dragDest_ draggingEntered:sender view:self];
 }
 
 - (void)draggingExited:(id<NSDraggingInfo>)sender {
   [dragDest_ draggingExited:sender];
 }
 
@@ skipping 30 matching lines @@
       [[[notification userInfo] objectForKey:kSelectionDirection]
         unsignedIntegerValue];
   if (direction == NSDirectSelection)
     return;
 
   [self webContents]->
       FocusThroughTabTraversal(direction == NSSelectingPrevious);
 }
 
 @end