Simplify PDFium by removing code that's not used in the open source repo.

core/src/fxcodec/libjpeg/fpdfapi_jerror.c

 #if !defined(_FX_JPEG_TURBO_)
 /*
  * jerror.c
  *
  * Copyright (C) 1991-1998, Thomas G. Lane.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains simple error-reporting and trace-message routines.
  * These are suitable for Unix-like systems and others where writing to
  * stderr is the right thing to do.  Many applications will want to replace
  * some or all of these routines.
  *
- * If you define USE_WINDOWS_MESSAGEBOX in jconfig.h or in the makefile,
- * you get a Windows-specific hack to display error messages in a dialog box.
- * It ain't much, but it beats dropping error messages into the bit bucket,
- * which is what happens to output to stderr under most Windows C compilers.
- *
  * These routines are used by both the compression and decompression code.
  */
 
 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jversion.h"
 #include "jerror.h"
 
 #ifndef EXIT_FAILURE            /* define exit() codes if not provided */
@@ skipping 63 matching lines @@
  */
 
 METHODDEF(void)
 output_message (j_common_ptr cinfo)
 {
   char buffer[JMSG_LENGTH_MAX];
 
   /* Create the message */
   (*cinfo->err->format_message) (cinfo, buffer);
 
-#ifdef USE_WINDOWS_MESSAGEBOX
-  /* Display it in a message dialog box */
-  MessageBox(GetActiveWindow(), buffer, "JPEG Library Error",
-             MB_OK | MB_ICONERROR);
-#else
   /* Send it to stderr, adding a newline */
-#ifndef _FPDFAPI_MINI_
   FXSYS_fprintf(stderr, "%s\n", buffer);
-#endif
-#endif
 }
 
 
 /*
  * Decide whether to emit a trace or warning message.
  * msg_level is one of:
  *   -1: recoverable corrupt-data warning, may want to abort.
  *    0: important advisory messages (always display to user).
  *    1: first level of tracing detail.
  *    2,3,...: successively more detailed tracing messages.
@@ skipping 124 matching lines @@
   err->last_jpeg_message = (int) JMSG_LASTMSGCODE - 1;
 
   err->addon_message_table = NULL;
   err->first_addon_message = 0; /* for safety */
   err->last_addon_message = 0;
 
   return err;
 }
 
 #endif //_FX_JPEG_TURBO_