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

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

Index: webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
diff --git a/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc b/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
index 80936795a401296f9ea87855464faf8ce835c7a4..d8e139c6703c5ad30f4b9efba8aadf23d7b9f7f0 100644
--- a/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
+++ b/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
@@ -176,7 +176,7 @@ int HandleCommandLineFlags(webrtc::test::TestConfig* config) {
   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;
     }