Add sanity check for arrival timestamps.

webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc

Index: webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc b/webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc
index 194ef56b25ea3e6a28aa6cec4285b84bd540f866..20f3bbed6bad62531199c2e5e953c48fffe74c97 100644
--- a/webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc
+++ b/webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc
@@ -10,6 +10,8 @@
 
 #include "webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.h"
 
+#include <limits>
+
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/system_wrappers/include/clock.h"
@@ -23,6 +25,11 @@ namespace webrtc {
 const int RemoteEstimatorProxy::kDefaultProcessIntervalMs = 50;
 const int RemoteEstimatorProxy::kBackWindowMs = 500;
 
+// The maximum allowed value for a timestamp in milliseconds. This is lower
+// than the numerical limit since we often convert to microseconds.
+static constexpr int64_t kMaxTimeMs =
+    std::numeric_limits<int64_t>::max() / 1000;
+
 RemoteEstimatorProxy::RemoteEstimatorProxy(Clock* clock,
                                            PacketRouter* packet_router)
     : clock_(clock),
@@ -89,6 +96,11 @@ void RemoteEstimatorProxy::Process() {
 
 void RemoteEstimatorProxy::OnPacketArrival(uint16_t sequence_number,
                                            int64_t arrival_time) {
+  if (arrival_time < 0 || arrival_time > kMaxTimeMs) {
+    LOG(LS_WARNING) << "Arrival time out of bounds: " << arrival_time;
+    return;
+  }
+
   // TODO(holmer): We should handle a backwards wrap here if the first
   // sequence number was small and the new sequence number is large. The
   // SequenceNumberUnwrapper doesn't do this, so we should replace this with