Cast: Added missing DCHECKs to ThreadChecker calls and minor cleanup.

media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc

Index: media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc
diff --git a/media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc b/media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc
index 8158f8d2163c784792ccc2c2086fc7ca3b82fd94..a19c6a33be1adeb5bbe504729f53dc55410765b8 100644
--- a/media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc
+++ b/media/cast/rtcp/receiver_rtcp_event_subscriber_unittest.cc
@@ -17,7 +17,7 @@ namespace cast {
 
 namespace {
 
-const size_t kSizeThreshold = 10u;
+const size_t kMaxEventEntries = 10u;
 const int64 kDelayMs = 20L;
 
 }  // namespace
@@ -43,7 +43,7 @@ class ReceiverRtcpEventSubscriberTest : public ::testing::Test {
 
   void Init(ReceiverRtcpEventSubscriber::Type type) {
     event_subscriber_.reset(
-        new ReceiverRtcpEventSubscriber(task_runner_, kSizeThreshold, type));
+        new ReceiverRtcpEventSubscriber(kMaxEventEntries, type));
     cast_environment_->Logging()->AddRawEventSubscriber(
         event_subscriber_.get());
   }