Implement qpSum stat for video send ssrc stats.

webrtc/api/statscollector_unittest.cc

Index: webrtc/api/statscollector_unittest.cc
diff --git a/webrtc/api/statscollector_unittest.cc b/webrtc/api/statscollector_unittest.cc
index 782926bcee734b1ad868f4043d6fb14cc0b1cb9c..520722d892b0a4921d60d8c5aea1b4c20c1a8d70 100644
--- a/webrtc/api/statscollector_unittest.cc
+++ b/webrtc/api/statscollector_unittest.cc
@@ -1921,6 +1921,7 @@ TEST_F(StatsCollectorTest, VerifyVideoSendSsrcStats) {
   // Construct a stats value to read.
   video_sender_info.add_ssrc(1234);
   video_sender_info.frames_encoded = 10;
+  video_sender_info.qp_sum = rtc::Optional<uint64_t>(11);
   stats_read.senders.push_back(video_sender_info);
 
   EXPECT_CALL(session_, video_channel()).WillRepeatedly(Return(&video_channel));
@@ -1932,6 +1933,8 @@ TEST_F(StatsCollectorTest, VerifyVideoSendSsrcStats) {
   EXPECT_EQ(rtc::ToString(video_sender_info.frames_encoded),
             ExtractSsrcStatsValue(reports,
                                   StatsReport::kStatsValueNameFramesEncoded));
+  EXPECT_EQ(rtc::ToString(*video_sender_info.qp_sum),
+            ExtractSsrcStatsValue(reports, StatsReport::kStatsValueNameQpSum));
 }
 
 // This test verifies that stats are correctly set in video receive ssrc stats.