Fix bug where rtcp::TransportFeedback may generate incorrect messages.

webrtc/modules/rtp_rtcp/source/rtcp_packet/transport_feedback_unittest.cc

 /*
  *  Copyright (c) 2015 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.
  */
 
@@ skipping 436 matching lines @@
   ByteWriter<uint16_t>::WriteBigEndian(
       &mod_buffer[2], ByteReader<uint16_t>::ReadBigEndian(&mod_buffer[2]) +
                           ((kPaddingBytes + 3) / 4));
 
   rtc::scoped_ptr<TransportFeedback> parsed_packet(
       TransportFeedback::ParseFrom(mod_buffer, kExpectedSizeWithPadding));
   ASSERT_TRUE(parsed_packet.get() != nullptr);
   EXPECT_EQ(kExpectedSizeWords * 4, packet->Length());  // Padding not included.
 }
 
+TEST(RtcpPacketTest, TransportFeedback_HeyWhatsGoingOn) {

[stefan-webrtc, 2015/09/30 10:45:27]

There must be a better name than this? :)

[sprang_webrtc, 2015/09/30 11:09:27]

Oops. Fixed. :)

+  const int kOneBitVectorCapacity = 14;
+  const int kTwoBitVectorCapacity = 7;
+  const int64_t kLargeTimeDelta =
+      TransportFeedback::kDeltaScaleFactor * (1 << 8);
+
+  // Test that a number of small deltas followed by a large delta results in a
+  // correct split into multiple chunks, as needed.
+
+  for (int num_small_deltas = kTwoBitVectorCapacity - 1;

[stefan-webrtc, 2015/09/30 10:45:27]

I don't follow why you don't start this counter on 0. Probably because I have
forgotten the details already... :/

[sprang_webrtc, 2015/09/30 11:09:27]

Nah, only that that range wasn't quite so suspect. Originally I only tested the
one case that triggered the crash bug. Can change it to 0 just to be sure.

+       num_small_deltas <= kOneBitVectorCapacity + 1; ++num_small_deltas) {
+    TransportFeedback feedback;
+    feedback.WithBase(0, 0);
+    for (int i = 0; i < num_small_deltas; ++i)
+      feedback.WithReceivedPacket(i, i * 1000);
+    feedback.WithReceivedPacket(num_small_deltas,
+                                num_small_deltas * 1000 + kLargeTimeDelta);
+
+    rtc::scoped_ptr<rtcp::RawPacket> serialized_packet = feedback.Build();
+    EXPECT_TRUE(serialized_packet.get() != nullptr);
+    rtc::scoped_ptr<TransportFeedback> deserialized_packet =
+        TransportFeedback::ParseFrom(serialized_packet->Buffer(),
+                                     serialized_packet->Length());
+    EXPECT_TRUE(deserialized_packet.get() != nullptr);
+  }
+}
+
 }  // namespace
 }  // namespace webrtc