Add support for 3-byte headers in VideoToolbox NALU parser.

webrtc/common_video/h264/h264_common.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/common_video/h264/h264_common.h"
 
 namespace webrtc {
 namespace H264 {
 
 const uint8_t kNaluTypeMask = 0x1F;
 
 std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer,
                                        size_t buffer_size) {
   // This is sorta like Boyer-Moore, but with only the first optimization step:
   // given a 3-byte sequence we're looking at, if the 3rd byte isn't 1 or 0,
   // skip ahead to the next 3-byte sequence. 0s and 1s are relatively rare, so
   // this will skip the majority of reads/checks.
-  RTC_CHECK_GE(buffer_size, kNaluShortStartSequenceSize);
   std::vector<NaluIndex> sequences;
+  if (buffer_size < kNaluShortStartSequenceSize)
+    return sequences;
   const size_t end = buffer_size - kNaluShortStartSequenceSize;
   for (size_t i = 0; i < end;) {
     if (buffer[i + 2] > 1) {
       i += 3;
     } else if (buffer[i + 2] == 1 && buffer[i + 1] == 0 && buffer[i] == 0) {
       // We found a start sequence, now check if it was a 3 of 4 byte one.
       NaluIndex index = {i, i + 3, 0};
       if (index.start_offset > 0 && buffer[index.start_offset - 1] == 0)
         --index.start_offset;
 
@@ skipping 62 matching lines @@
     if (byte == 0) {
       ++num_consecutive_zeros;
     } else {
       num_consecutive_zeros = 0;
     }
   }
 }
 
 }  // namespace H264
 }  // namespace webrtc