Fix implicite cast from signed int to unsigned int in unittest.cc
BUG=3636
TESTED=set GYP_DEFINES=target_arch=ia32 & call python webrtc\build\gyp_webrtc -G msvs_version=2013 & ninja -C out\Debug
R=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20069004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6827 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/modules/video_coding/codecs/test_framework/unit_test.cc b/modules/video_coding/codecs/test_framework/unit_test.cc
index ec12a51..ab8d4d2 100644
--- a/modules/video_coding/codecs/test_framework/unit_test.cc
+++ b/modules/video_coding/codecs/test_framework/unit_test.cc
@@ -393,7 +393,7 @@
     _inst.maxFramerate = 30;
 
     // Bad bitrate.
-    _inst.startBitrate = -1;
+    _inst.startBitrate = static_cast<unsigned int>(-1);
     EXPECT_TRUE(_encoder->InitEncode(&_inst, 1, 1440) ==
         WEBRTC_VIDEO_CODEC_ERR_PARAMETER);
     _inst.maxBitrate = _inst.startBitrate - 1;