Make mixing test die earlier on failure instead of spamming errors

This test currently takes 288 seconds to fail if output values are
wrong; there's no point to print the failure hundreds of times.
This change will exit the test early.

R=henrika@webrtc.org
BUG=623538
NOTRY=true

Review-Url: https://codereview.webrtc.org/2097363002
Cr-Original-Commit-Position: refs/heads/master@{#13295}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 685440be2dd3bcb996babfcd4ee31b8b71100436
diff --git a/voice_engine/test/auto_test/standard/mixing_test.cc b/voice_engine/test/auto_test/standard/mixing_test.cc
index b7f7d56..fcee2f7 100644
--- a/voice_engine/test/auto_test/standard/mixing_test.cc
+++ b/voice_engine/test/auto_test/standard/mixing_test.cc
@@ -129,8 +129,8 @@
       std::ostringstream trace_stream;
       trace_stream << samples_read << " samples read";
       SCOPED_TRACE(trace_stream.str());
-      EXPECT_LE(output_value, max_output_value);
-      EXPECT_GE(output_value, min_output_value);
+      ASSERT_LE(output_value, max_output_value);
+      ASSERT_GE(output_value, min_output_value);
     }
     // Ensure we've at least recorded half as much file as the duration of the
     // test. We have to use a relaxed tolerance here due to filesystem flakiness