Make FakeDecodeFromFile handle codec-internal CNG

webrtc/modules/audio_coding/neteq/tools/packet.cc

Index: webrtc/modules/audio_coding/neteq/tools/packet.cc
diff --git a/webrtc/modules/audio_coding/neteq/tools/packet.cc b/webrtc/modules/audio_coding/neteq/tools/packet.cc
index 46fd0cbc8cd531a1ea6b8d7d4a684388bdeeb3e2..a31d080146c5c9ff5b4fc3ff38956ec4f891a854 100644
--- a/webrtc/modules/audio_coding/neteq/tools/packet.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/packet.cc
@@ -14,6 +14,7 @@
 
 #include <memory>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_header_parser.h"
 
@@ -142,6 +143,7 @@ bool Packet::ParseHeader(const RtpHeaderParser& parser) {
   payload_ = &payload_memory_[header_.headerLength];
   assert(packet_length_bytes_ >= header_.headerLength);
   payload_length_bytes_ = packet_length_bytes_ - header_.headerLength;
+  RTC_CHECK_GE(virtual_packet_length_bytes_, packet_length_bytes_);
   assert(virtual_packet_length_bytes_ >= header_.headerLength);
   virtual_payload_length_bytes_ =
       virtual_packet_length_bytes_ - header_.headerLength;