Update the alpha value in the echo detector.

webrtc/modules/audio_processing/residual_echo_detector_unittest.cc

Index: webrtc/modules/audio_processing/residual_echo_detector_unittest.cc
diff --git a/webrtc/modules/audio_processing/residual_echo_detector_unittest.cc b/webrtc/modules/audio_processing/residual_echo_detector_unittest.cc
index 7f6cf16abd57af5c7e5bb33db4c9efd6541eab97..9ba3bf4e401306f02312a673e6f8916a7c79e75e 100644
--- a/webrtc/modules/audio_processing/residual_echo_detector_unittest.cc
+++ b/webrtc/modules/audio_processing/residual_echo_detector_unittest.cc
@@ -88,8 +88,8 @@ TEST(ResidualEchoDetectorTests, EchoWithRenderClockDrift) {
   // render buffer, clock drift can only be discovered after a certain delay.
   // A growing buffer can be caused by jitter or clock drift and it's not
   // possible to make this decision right away. For this reason we only expect
-  // an echo likelihood of 80% in this test.
-  EXPECT_GT(echo_detector.echo_likelihood(), 0.8f);
+  // an echo likelihood of 75% in this test.
+  EXPECT_GT(echo_detector.echo_likelihood(), 0.75f);
 }
 
 TEST(ResidualEchoDetectorTests, EchoWithCaptureClockDrift) {