Make v8 embedder data slot configurable

public/fpdf_formfill.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef PUBLIC_FPDF_FORMFILL_H_
 #define PUBLIC_FPDF_FORMFILL_H_
 
 #include "fpdfview.h"
@@ skipping 213 matching lines @@
     *   pointer to FPDF_FORMFILLINFO interface.
     **/
     void*   m_pFormfillinfo;
 
     /* Version 2. */
 
     /**
     *   pointer to the v8::Isolate to use, or NULL to force PDFium to create one.
     **/
     void*   m_isolate;
+
+    /**
+     *   The embedder data slot to use in the v8::Isolate.

[Tom Sepez, 2015/07/15 22:27:57]

nit: need a better comment here, as in what to pass if you're not sure, or why
you would change it, otherwise embedders might have trouble.

+     */
+    unsigned int m_v8EmbedderSlot;
 } IPDF_JSPLATFORM;
 
 // Flags for Cursor type
 #define FXCT_ARROW  0
 #define FXCT_NESW   1
 #define FXCT_NWSE   2
 #define FXCT_VBEAM  3
 #define FXCT_HBEAM  4
 #define FXCT_HAND   5
 
@@ skipping 591 matching lines @@
 **/
 DLLEXPORT void STDCALL FPDF_FFLDraw(FPDF_FORMHANDLE hHandle,FPDF_BITMAP bitmap, FPDF_PAGE page, int start_x, int start_y,
                         int size_x, int size_y, int rotate, int flags);
 
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif  // PUBLIC_FPDF_FORMFILL_H_