Fixed bug in PacketBuffer to correctly detect new complete frames after ClearTo has been called.

BUG=webrtc:5514
R=stefan@webrtc.org, terelius@webrtc.org

Review URL: https://codereview.webrtc.org/2527903002 .

Cr-Commit-Position: refs/heads/master@{#15269}
diff --git a/webrtc/modules/video_coding/video_packet_buffer_unittest.cc b/webrtc/modules/video_coding/video_packet_buffer_unittest.cc
index 6dc4e8f..a937af6 100644
--- a/webrtc/modules/video_coding/video_packet_buffer_unittest.cc
+++ b/webrtc/modules/video_coding/video_packet_buffer_unittest.cc
@@ -425,5 +425,18 @@
   EXPECT_FALSE(frames_from_callback_.begin()->second->GetBitstream(nullptr));
 }
 
+TEST_F(TestPacketBuffer, FramesAfterClear) {
+  Insert(9025, kDeltaFrame, kFirst, kLast);
+  Insert(9024, kKeyFrame, kFirst, kLast);
+  packet_buffer_->ClearTo(9025);
+  Insert(9057, kDeltaFrame, kFirst, kLast);
+  Insert(9026, kDeltaFrame, kFirst, kLast);
+
+  CheckFrame(9024);
+  CheckFrame(9025);
+  CheckFrame(9026);
+  CheckFrame(9057);
+}
+
 }  // namespace video_coding
 }  // namespace webrtc