Restore severity precondition to logging.h.

I mistakenly ommitted the checks when logging.h was ported from
libjingle to webrtc. This caused a significant CPU cost for logs which
were later filtered out anyway.

Verified with LS_VERBOSE logging in neteq4, running:
$ out/Release/modules_unittests \
--gtest_filter=NetEqDecodingTest.TestBitExactness \
--gtest_repeat=50 > time.txt
$ grep "case ran" time.txt | grep "[0-9]* ms" -o | sort

Results on a MacBook Retina, averaged over 5 runs:
Verbose logs disabled:                          666 ms
Exisiting implementation, verbose logs enabled: 944 ms (1.42x)
New implementation, verbose logs enabled:       673 ms (1.01x)

BUG=2314
R=henrik.lundin@webrtc.org, henrike@webrtc.org, kjellander@webrtc.org, turaj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2160005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4682 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/neteq4/tools/neteq_rtpplay.cc

@@ -145,7 +145,7 @@ int main(int argc, char* argv[]) {
   webrtc::Trace::CreateTrace();
   webrtc::Trace::SetTraceFile((webrtc::test::OutputPath() +
       "neteq_trace.txt").c_str());
-  webrtc::Trace::SetLevelFilter(webrtc::kTraceAll);
+  webrtc::Trace::set_level_filter(webrtc::kTraceAll);
 
   // Initialize NetEq instance.
   int sample_rate_hz = 16000;