Add a placeholder stat for logging the estimated residual echo likelihood.

The stat is currently always set to zero until the residual echo detector has landed.

BUG=webrtc:6525

Review-Url: https://codereview.webrtc.org/2431443003
Cr-Commit-Position: refs/heads/master@{#14721}
diff --git a/webrtc/api/statscollector_unittest.cc b/webrtc/api/statscollector_unittest.cc
index 8d5978f..866e76f 100644
--- a/webrtc/api/statscollector_unittest.cc
+++ b/webrtc/api/statscollector_unittest.cc
@@ -402,8 +402,13 @@
       &value_in_report));
   EXPECT_EQ(rtc::ToString<int>(sinfo.echo_return_loss_enhancement),
             value_in_report);
-  EXPECT_TRUE(GetValue(
-      report, StatsReport::kStatsValueNameAudioInputLevel, &value_in_report));
+  EXPECT_TRUE(GetValue(report,
+                       StatsReport::kStatsValueNameResidualEchoLikelihood,
+                       &value_in_report));
+  EXPECT_EQ(rtc::ToString<float>(sinfo.residual_echo_likelihood),
+            value_in_report);
+  EXPECT_TRUE(GetValue(report, StatsReport::kStatsValueNameAudioInputLevel,
+                       &value_in_report));
   EXPECT_EQ(rtc::ToString<int>(sinfo.audio_level), value_in_report);
   EXPECT_TRUE(GetValue(
       report, StatsReport::kStatsValueNameTypingNoiseState, &value_in_report));