Reduce the runtime of some ACM tests in modules_tests

webrtc/modules/audio_coding/test/TestRedFec.cc

Index: webrtc/modules/audio_coding/test/TestRedFec.cc
diff --git a/webrtc/modules/audio_coding/test/TestRedFec.cc b/webrtc/modules/audio_coding/test/TestRedFec.cc
index d54402657f402a5fadda0cc3c0369ca9f80b90a5..a1bdc04e5314b06d985c31de4e2ecec81068a4e2 100644
--- a/webrtc/modules/audio_coding/test/TestRedFec.cc
+++ b/webrtc/modules/audio_coding/test/TestRedFec.cc
@@ -453,6 +453,10 @@ int16_t TestRedFec::RegisterSendCodec(char side, const char* codecName,
 void TestRedFec::Run() {
   AudioFrame audioFrame;
   int32_t outFreqHzB = _outFileB.SamplingFrequency();
+  // Set test length to 500 ms (50 blocks of 10 ms each).
+  _inFileA.SetNum10MsBlocksToRead(50);
+  // Fast-forward 1 second (100 blocks) since the file starts with silence.
+  _inFileA.FastForward(100);
 
   while (!_inFileA.EndOfFile()) {
     EXPECT_GT(_inFileA.Read10MsData(audioFrame), 0);