[rtp_rtcp] fixed namespaces lint warnings

webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc b/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
index 7eaeca1ea09cf654a31d23f1bf8a23b302f46488..a639f7f7f572940c1d2f1782decffe9108b1a51b 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
@@ -21,10 +21,9 @@
 #include "webrtc/test/null_transport.h"
 #include "webrtc/typedefs.h"
 
+namespace webrtc {
 namespace {
 
-using namespace webrtc;
-
 class TestTransport : public Transport {
  public:
   TestTransport(RTCPReceiver* rtcp_receiver) : rtcp_receiver_(rtcp_receiver) {}
@@ -130,3 +129,4 @@ TEST_F(RtcpFormatRembTest, TestCompund) {
   EXPECT_EQ(0, rtcp_sender_->SendRTCP(feedback_state, kRtcpRemb));
 }
 }  // namespace
+}  // namespace webrtc