Mark drags starting in web content as tainted to avoid file path forgery

content/browser/web_contents/web_drag_dest_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 "content/browser/web_contents/web_drag_dest_mac.h"
 
 #import <Carbon/Carbon.h>
 
 #include "base/strings/sys_string_conversions.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
@@ skipping 235 matching lines @@
 
 // Given |data|, which should not be nil, fill it in using the contents of the
 // given pasteboard. The types handled by this method should be kept in sync
 // with [WebContentsViewCocoa registerDragTypes].
 - (void)populateDropData:(DropData*)data
           fromPasteboard:(NSPasteboard*)pboard {
   DCHECK(data);
   DCHECK(pboard);
   NSArray* types = [pboard types];
 
+  data->did_originate_from_renderer =
+      [types containsObject:ui::kChromeDragDummyPboardType];
+
   // Get URL if possible. To avoid exposing file system paths to web content,
   // filenames in the drag are not converted to file URLs.
   ui::PopulateURLAndTitleFromPasteboard(&data->url,
                                         &data->url_title,
                                         pboard,
                                         NO);
 
   // Get plain text.
   if ([types containsObject:NSStringPboardType]) {
     data->text = base::NullableString16(
@@ skipping 35 matching lines @@
   // Get custom MIME data.
   if ([types containsObject:ui::kWebCustomDataPboardType]) {
     NSData* customData = [pboard dataForType:ui::kWebCustomDataPboardType];
     ui::ReadCustomDataIntoMap([customData bytes],
                               [customData length],
                               &data->custom_data);
   }
 }
 
 @end