Fix two simple type mismatches thay may cause compilation issues on win.

webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 158 matching lines @@
     fprintf(stderr, "Cannot find output directory: %s\n",
             FLAGS_output_dir.c_str());
     return 3;
   }
   config->output_dir = FLAGS_output_dir;
 
   // Manufacture an output filename if none was given.
   if (FLAGS_output_filename.empty()) {
     // Cut out the filename without extension from the given input file
     // (which may include a path)
-    int startIndex = FLAGS_input_filename.find_last_of("/") + 1;
+    size_t startIndex = FLAGS_input_filename.find_last_of("/") + 1;
     if (startIndex == 0) {
       startIndex = 0;
     }
     FLAGS_output_filename =
         FLAGS_input_filename.substr(
             startIndex, FLAGS_input_filename.find_last_of(".") - startIndex) +
         "_out.yuv";
   }
 
   // Verify output file can be written.
@@ skipping 358 matching lines @@
   }
   if (FLAGS_python) {
     PrintPythonOutput(config, stats, ssim_result, psnr_result);
   }
   delete processor;
   delete encoder;
   delete decoder;
   Log("Quality test finished!");
   return 0;
 }