Reduce the runtime of some ACM tests in modules_tests

webrtc/modules/audio_coding/test/TestVADDTX.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 69 matching lines @@
 // Encoding a file and see if the numbers that various packets occur follow
 // the expectation.
 void TestVadDtx::Run(std::string in_filename, int frequency, int channels,
                      std::string out_filename, bool append,
                      const int* expects) {
   monitor_->ResetStatistics();
 
   PCMFile in_file;
   in_file.Open(in_filename, frequency, "rb");
   in_file.ReadStereo(channels > 1);
+  // Set test length to 1000 ms (100 blocks of 10 ms each).
+  in_file.SetNum10MsBlocksToRead(100);
+  // Fast-forward both files 500 ms (50 blocks). The first second of the file is
+  // silence, but we want to keep half of that to test silence periods.
+  in_file.FastForward(50);
 
   PCMFile out_file;
   if (append) {
     out_file.Open(out_filename, kOutputFreqHz, "ab");
   } else {
     out_file.Open(out_filename, kOutputFreqHz, "wb");
   }
 
   uint16_t frame_size_samples = in_file.PayloadLength10Ms();
   uint32_t time_stamp = 0x12345678;
@@ skipping 162 matching lines @@
 
   EXPECT_EQ(0, acm_send_->EnableOpusDtx());
 
   expects[kEmptyFrame] = 1;
   Run(webrtc::test::ResourcePath("audio_coding/teststereo32kHz", "pcm"),
       32000, 2, out_filename, true, expects);
 #endif
 }
 
 }  // namespace webrtc