Add APIs for limited use of document tagged code.

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_
 
 // NOLINTNEXTLINE(build/include)
@@ skipping 131 matching lines @@
   *           filePath    -   The string buffer to receive the file path. Can be
   * NULL.
   *           length      -   The length of the buffer, number of bytes. Can be
   * 0.
   * Return Value:
   *       Number of bytes the filePath consumes, including trailing zeros.
   * Comments:
   *       The filePath should be always input in local encoding.
   *
   *       The return value always indicated number of bytes required for the
-  * buffer, even when there is
-  *       no buffer specified, or the buffer size is less then required. In this
-  * case, the buffer will not
-  *       be modified.
+  *       buffer , even when there is no buffer specified, or the buffer size is
+  *       less than required. In this case, the buffer will not be modified.
   */
   int (*Doc_getFilePath)(struct _IPDF_JsPlatform* pThis,
                          void* filePath,
                          int length);
 
   /*
   * Method: Doc_mail
   *           Mails the data buffer as an attachment to all recipients, with or
   * without user interaction.
   * Interface Version:
@@ skipping 1591 matching lines @@
 FPDF_StringHandleAddString(FPDF_STRINGHANDLE stringHandle,
                            FPDF_BYTESTRING bsText,
                            FPDF_DWORD size);
 #endif  // PDF_ENABLE_XFA
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif  // PUBLIC_FPDF_FORMFILL_H_