Additional window features are not passed as a parameter to new popup windows

content/common/view_messages.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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 345 matching lines @@
   // The URL that will be loaded in the new window (empty if none has been
   // sepcified).
   IPC_STRUCT_MEMBER(GURL, target_url)
 
   // The referrer that will be used to load |target_url| (empty if none has
   // been specified).
   IPC_STRUCT_MEMBER(content::Referrer, referrer)
 
   // The window features to use for the new view.
   IPC_STRUCT_MEMBER(blink::WebWindowFeatures, features)
+
+  // The additional window features to use for the new view.

[jam, 2013/11/11 17:07:18]

nit: add a comment to explain that although this is part of
blink::WebWindowFeatures, we send it separately because we can't send WebStrings
over IPCs

+  IPC_STRUCT_MEMBER(std::vector<string16>, additional_features)
 IPC_STRUCT_END()
 
 IPC_STRUCT_BEGIN(ViewHostMsg_CreateWorker_Params)
   // URL for the worker script.
   IPC_STRUCT_MEMBER(GURL, url)
 
   // Name for a SharedWorker, otherwise empty string.
   IPC_STRUCT_MEMBER(string16, name)
 
   // The ID of the parent document (unique within parent renderer).
@@ skipping 2003 matching lines @@
 // synchronously (see crbug.com/120597). This IPC message sends the character
 // bounds after every composition change to always have correct bound info.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.