Be able to build cast_unittest and related targets in Chrome tree

media/cast/rtcp/test_rtcp_packet_builder.cc

Index: media/cast/rtcp/test_rtcp_packet_builder.cc
diff --git a/media/cast/rtcp/test_rtcp_packet_builder.cc b/media/cast/rtcp/test_rtcp_packet_builder.cc
index d6468e53a4eba569a7710c8cc7322fb0d42682b3..c3938bdda09ebfb13e7282748941f77493c17c87 100644
--- a/media/cast/rtcp/test_rtcp_packet_builder.cc
+++ b/media/cast/rtcp/test_rtcp_packet_builder.cc
@@ -45,7 +45,8 @@ void TestRtcpPacketBuilder::AddSdesCname(uint32 sender_ssrc,
   AddRtcpHeader(202, 1);
   big_endian_writer_.WriteU32(sender_ssrc);
   big_endian_writer_.WriteU8(1);  // c_name.
-  big_endian_writer_.WriteU8(c_name.size());  // c_name length in bytes.
+  big_endian_writer_.WriteU8(
+      static_cast<uint8>(c_name.size()));  // c_name length in bytes.
   for (size_t i = 0; i < c_name.size(); ++i) {
     big_endian_writer_.WriteU8(c_name.c_str()[i]);
   }