Adjust threshold for datarate frame drop test.

Current threshold is little too strict.

Change-Id: I99ec1409d095e0c2fd3b7ab398742cabcc05700b
diff --git a/test/datarate_test.cc b/test/datarate_test.cc
index b6cae79..7d8a0ab 100644
--- a/test/datarate_test.cc
+++ b/test/datarate_test.cc
@@ -538,7 +538,7 @@
         << " The first dropped frame for drop_thresh " << i
         << " > first dropped frame for drop_thresh "
         << i - kDropFrameThreshTestStep;
-    ASSERT_GE(num_drops_, last_num_drops * 0.90)
+    ASSERT_GE(num_drops_, last_num_drops * 0.85)
         << " The number of dropped frames for drop_thresh " << i
         << " < number of dropped frames for drop_thresh "
         << i - kDropFrameThreshTestStep;