Add functions to interact with ASan and MSan, and some sample uses

The sample uses are from when I debugged bug 617124. The change in neteq_network_stats_unittest.cc is a fix for a minor unrelated bug found by the try bots when I tried to land this CL (a test was passing uninitialized packet data to NetEq).

BUG=chromium:617124

Review-Url: https://codereview.webrtc.org/2293893002
Cr-Commit-Position: refs/heads/master@{#14034}

webrtc/modules/audio_coding/neteq/neteq_impl.cc

@@ -19,6 +19,7 @@
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/safe_conversions.h"
+#include "webrtc/base/sanitizer.h"
 #include "webrtc/base/trace_event.h"
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 #include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
@@ -132,6 +133,7 @@ NetEqImpl::~NetEqImpl() = default;
 int NetEqImpl::InsertPacket(const WebRtcRTPHeader& rtp_header,
                             rtc::ArrayView<const uint8_t> payload,
                             uint32_t receive_timestamp) {
+  rtc::MsanCheckInitialized(payload);
   TRACE_EVENT0("webrtc", "NetEqImpl::InsertPacket");
   rtc::CritScope lock(&crit_sect_);
   int error =