Allow parsing empty RTCP TargetBitrate messages, but stop sending them.

webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc b/webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc
index 1c8f39de61d58541084f12346cf5a6b18d25f23f..2c5098d274018766f8bff673a6f26c662bb59e68 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_packet/target_bitrate_unittest.cc
@@ -54,7 +54,7 @@ void CheckBitrateItems(const std::vector<BitrateItem>& bitrates) {
 
 TEST(TargetBitrateTest, Parse) {
   TargetBitrate target_bitrate;
-  EXPECT_TRUE(target_bitrate.Parse(kPacket, kPacketLengthBlocks));
+  target_bitrate.Parse(kPacket, kPacketLengthBlocks);
   CheckBitrateItems(target_bitrate.GetTargetBitrates());
 }
 
@@ -86,4 +86,11 @@ TEST(TargetBitrateTest, Create) {
   EXPECT_EQ(0, memcmp(kPacket, buffer, sizeof(kPacket)));
 }
 
+TEST(TargetBitrateTest, ParseNullBitratePacket) {
+  const uint8_t kNullPacket[] = {TargetBitrate::kBlockType, 0x00, 0x00, 0x00};
+  TargetBitrate target_bitrate;
+  target_bitrate.Parse(kNullPacket, 0);
+  EXPECT_TRUE(target_bitrate.GetTargetBitrates().empty());
+}
+
 }  // namespace webrtc