PacketBuffer is now ref counted.

Since all FrameObjects have a reference to its PacketBuffer and since
the PacketBuffer can be thrown away at any moment the PacketBuffer
has to be ref counted in order to avoid FrameObjects dereferencing a potentially
destroyed object.

BUG=webrtc:5514
R=danilchap@webrtc.org, mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://codereview.webrtc.org/2199133004 .

Cr-Commit-Position: refs/heads/master@{#13725}
diff --git a/webrtc/modules/video_coding/packet_buffer.cc b/webrtc/modules/video_coding/packet_buffer.cc
index df17350..0d36b9c 100644
--- a/webrtc/modules/video_coding/packet_buffer.cc
+++ b/webrtc/modules/video_coding/packet_buffer.cc
@@ -12,7 +12,9 @@
 
 #include <algorithm>
 #include <limits>
+#include <utility>
 
+#include "webrtc/base/atomicops.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/video_coding/frame_object.h"
@@ -21,10 +23,19 @@
 namespace webrtc {
 namespace video_coding {
 
+rtc::scoped_refptr<PacketBuffer> PacketBuffer::Create(
+    Clock* clock,
+    size_t start_buffer_size,
+    size_t max_buffer_size,
+    OnReceivedFrameCallback* received_frame_callback) {
+  return rtc::scoped_refptr<PacketBuffer>(new PacketBuffer(
+      clock, start_buffer_size, max_buffer_size, received_frame_callback));
+}
+
 PacketBuffer::PacketBuffer(Clock* clock,
                            size_t start_buffer_size,
                            size_t max_buffer_size,
-                           OnCompleteFrameCallback* frame_callback)
+                           OnReceivedFrameCallback* received_frame_callback)
     : clock_(clock),
       size_(start_buffer_size),
       max_size_(max_buffer_size),
@@ -33,13 +44,15 @@
       first_packet_received_(false),
       data_buffer_(start_buffer_size),
       sequence_buffer_(start_buffer_size),
-      reference_finder_(frame_callback) {
+      received_frame_callback_(received_frame_callback) {
   RTC_DCHECK_LE(start_buffer_size, max_buffer_size);
   // Buffer size must always be a power of 2.
   RTC_DCHECK((start_buffer_size & (start_buffer_size - 1)) == 0);
   RTC_DCHECK((max_buffer_size & (max_buffer_size - 1)) == 0);
 }
 
+PacketBuffer::~PacketBuffer() {}
+
 bool PacketBuffer::InsertPacket(const VCMPacket& packet) {
   rtc::CritScope lock(&crit_);
   uint16_t seq_num = packet.seqNum;
@@ -69,12 +82,6 @@
   if (AheadOf(seq_num, last_seq_num_))
     last_seq_num_ = seq_num;
 
-  // If this is a padding or FEC packet, don't insert it.
-  if (packet.sizeBytes == 0) {
-    reference_finder_.PaddingReceived(packet.seqNum);
-    return true;
-  }
-
   sequence_buffer_[index].frame_begin = packet.isFirstPacket;
   sequence_buffer_[index].frame_end = packet.markerBit;
   sequence_buffer_[index].seq_num = packet.seqNum;
@@ -169,7 +176,8 @@
       std::unique_ptr<RtpFrameObject> frame(
           new RtpFrameObject(this, start_seq_num, seq_num, frame_size,
                              max_nack_count, clock_->TimeInMilliseconds()));
-      reference_finder_.ManageFrame(std::move(frame));
+
+      received_frame_callback_->OnReceivedFrame(std::move(frame));
     }
 
     index = (index + 1) % size_;
@@ -239,5 +247,17 @@
   first_packet_received_ = false;
 }
 
+int PacketBuffer::AddRef() const {
+  return rtc::AtomicOps::Increment(&ref_count_);
+}
+
+int PacketBuffer::Release() const {
+  int count = rtc::AtomicOps::Decrement(&ref_count_);
+  if (!count) {
+    delete this;
+  }
+  return count;
+}
+
 }  // namespace video_coding
 }  // namespace webrtc