Use unsigned type for iteration to avoid int overflow.

core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
index c395283fc3a5d01619bf4bac87a14fc1391439d5..022d788c72d54d6efdc2d313d253741a2eb59b18 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
@@ -1,7 +1,7 @@
 // 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
 
 #include "../../../include/fpdfapi/fpdf_parser.h"
@@ -402,7 +402,7 @@ CFX_WideString PDF_DecodeText(FX_LPCBYTE src_data, FX_DWORD src_len, CFX_CharMap
     CFX_WideString result;
     if (src_len >= 2 && ((src_data[0] == 0xfe && src_data[1] == 0xff) || (src_data[0] == 0xff && src_data[1] == 0xfe))) {
         FX_BOOL bBE = src_data[0] == 0xfe;
-        int max_chars = (src_len - 2) / 2;
+        FX_DWORD max_chars = (src_len - 2) / 2;
         if (!max_chars) {
             return result;
         }
@@ -412,7 +412,7 @@ CFX_WideString PDF_DecodeText(FX_LPCBYTE src_data, FX_DWORD src_len, CFX_CharMap
         FX_LPWSTR dest_buf = result.GetBuffer(max_chars);
         FX_LPCBYTE uni_str = src_data + 2;
         int dest_pos = 0;
-        for (int i = 0; i < max_chars * 2; i += 2) {
+        for (FX_DWORD i = 0; i < max_chars * 2; i += 2) {
             FX_WORD unicode = bBE ? (uni_str[i] << 8 | uni_str[i + 1]) : (uni_str[i + 1] << 8 | uni_str[i]);
             if (unicode == 0x1b) {
                 i += 2;