Fixes for re-enabling more MSVC level 4 warnings: media/ edition

media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc

Index: media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc
diff --git a/media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc b/media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc
index 47c79139ffc7636218f5ff34c31a80f1cfbee2ac..b4478c37ee761d781d84f34ea69f5c35ba6faa5c 100644
--- a/media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc
+++ b/media/cast/rtp_receiver/rtp_parser/rtp_parser_unittest.cc
@@ -39,7 +39,7 @@ class RtpParserTest : public ::testing::Test {
   void ExpectParsesPacket() {
     RtpCastHeader parsed_header;
     const uint8* payload = NULL;
-    size_t payload_size = -1;
+    size_t payload_size = static_cast<size_t>(-1);
     EXPECT_TRUE(rtp_parser_.ParsePacket(
         packet_, kPacketLength, &parsed_header, &payload, &payload_size));
 
@@ -63,7 +63,7 @@ class RtpParserTest : public ::testing::Test {
   void ExpectDoesNotParsePacket() {
     RtpCastHeader parsed_header;
     const uint8* payload = NULL;
-    size_t payload_size = -1;
+    size_t payload_size = static_cast<size_t>(-1);
     EXPECT_FALSE(rtp_parser_.ParsePacket(
         packet_, kPacketLength, &parsed_header, &payload, &payload_size));
   }