Optimize ParseRbsp method in H264 bitstream parser.

webrtc/common_video/h264/pps_parser.cc

Index: webrtc/common_video/h264/pps_parser.cc
diff --git a/webrtc/common_video/h264/pps_parser.cc b/webrtc/common_video/h264/pps_parser.cc
index b2860c221fdbea48268539daabc3d9f6c95f0970..73ad0cd5689721b44f896bc38068e146d4b555c5 100644
--- a/webrtc/common_video/h264/pps_parser.cc
+++ b/webrtc/common_video/h264/pps_parser.cc
@@ -11,6 +11,7 @@
 #include "webrtc/common_video/h264/pps_parser.h"
 
 #include <memory>
+#include <vector>
 
 #include "webrtc/common_video/h264/h264_common.h"
 #include "webrtc/base/bitbuffer.h"
@@ -38,8 +39,8 @@ rtc::Optional<PpsParser::PpsState> PpsParser::ParsePps(const uint8_t* data,
   // First, parse out rbsp, which is basically the source buffer minus emulation
   // bytes (the last byte of a 0x00 0x00 0x03 sequence). RBSP is defined in
   // section 7.3.1 of the H.264 standard.
-  std::unique_ptr<rtc::Buffer> unpacked_buffer = H264::ParseRbsp(data, length);
-  rtc::BitBuffer bit_buffer(unpacked_buffer->data(), unpacked_buffer->size());
+  std::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
+  rtc::BitBuffer bit_buffer(unpacked_buffer.data(), unpacked_buffer.size());
   return ParseInternal(&bit_buffer);
 }
 
@@ -52,15 +53,15 @@ bool PpsParser::ParsePpsIds(const uint8_t* data,
   // First, parse out rbsp, which is basically the source buffer minus emulation
   // bytes (the last byte of a 0x00 0x00 0x03 sequence). RBSP is defined in
   // section 7.3.1 of the H.264 standard.
-  std::unique_ptr<rtc::Buffer> unpacked_buffer = H264::ParseRbsp(data, length);
-  rtc::BitBuffer bit_buffer(unpacked_buffer->data(), unpacked_buffer->size());
+  std::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
+  rtc::BitBuffer bit_buffer(unpacked_buffer.data(), unpacked_buffer.size());
   return ParsePpsIdsInternal(&bit_buffer, pps_id, sps_id);
 }
 
 rtc::Optional<uint32_t> PpsParser::ParsePpsIdFromSlice(const uint8_t* data,
                                                        size_t length) {
-  std::unique_ptr<rtc::Buffer> slice_rbsp(H264::ParseRbsp(data, length));
-  rtc::BitBuffer slice_reader(slice_rbsp->data(), slice_rbsp->size());
+  std::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
+  rtc::BitBuffer slice_reader(unpacked_buffer.data(), unpacked_buffer.size());
 
   uint32_t golomb_tmp;
   // first_mb_in_slice: ue(v)