Cast: Let the extension control if DSCP is on or off.

media/cast/test/end2end_unittest.cc

Index: media/cast/test/end2end_unittest.cc
diff --git a/media/cast/test/end2end_unittest.cc b/media/cast/test/end2end_unittest.cc
index 0580d2cf8bc5e15c302388db642986364a340357..a650809ee0cf647022a8199a96105141ccd2cf2f 100644
--- a/media/cast/test/end2end_unittest.cc
+++ b/media/cast/test/end2end_unittest.cc
@@ -596,6 +596,7 @@ class End2EndTest : public ::testing::Test {
         NULL,
         testing_clock_sender_,
         dummy_endpoint,
+        "",
         base::Bind(&UpdateCastTransportStatus),
         base::Bind(&End2EndTest::LogRawEvents, base::Unretained(this)),
         base::TimeDelta::FromMilliseconds(1),