Fix a few windows compile warnings

samples/pdfium_test.cc

 // Copyright (c) 2010 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.
 
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include <list>
@@ skipping 250 matching lines @@
   }
   printf("Unsupported feature: %s.\n", feature.c_str());
 }
 
 bool ParseCommandLine(const std::vector<std::string>& args,
                       Options* options, std::list<std::string>* files) {
   if (args.empty()) {
     return false;
   }
   options->exe_path = args[0];
-  int cur_idx = 1;
+  size_t cur_idx = 1;
   for (; cur_idx < args.size(); ++cur_idx) {
     const std::string& cur_arg = args[cur_idx];
     if (cur_arg == "--ppm") {
       if (options->output_format != OUTPUT_NONE) {
         fprintf(stderr, "Duplicate or conflicting --ppm argument\n");
         return false;
       }
       options->output_format = OUTPUT_PPM;
     }
 #ifdef _WIN32
@@ skipping 21 matching lines @@
       options->bin_directory = cur_arg.substr(10);
     }
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
     else
       break;
   }
   if (cur_idx >= args.size()) {
     fprintf(stderr, "No input files.\n");
     return false;
   }
-  for (int i = cur_idx; i < args.size(); i++) {
+  for (size_t i = cur_idx; i < args.size(); i++) {
     files->push_back(args[i]);
   }
   return true;
 }
 
 class TestLoader {
  public:
   TestLoader(const char* pBuf, size_t len);
 
   const char* m_pBuf;
@@ skipping 186 matching lines @@
     if (!file_contents)
       continue;
     RenderPdf(filename, file_contents, file_length, options.output_format);
     free(file_contents);
   }
 
   FPDF_DestroyLibrary();
 
   return 0;
 }