Make sure that ApmHelpersTest tests don't enter a tight loop.

webrtc/media/engine/apm_helpers_unittest.cc

 /*
  *  Copyright (c) 2017 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.
  */
 
 #include "webrtc/media/engine/apm_helpers.h"
 
 #include "webrtc/media/engine/webrtcvoe.h"
 #include "webrtc/modules/audio_coding/codecs/mock/mock_audio_decoder_factory.h"
 #include "webrtc/modules/audio_device/include/mock_audio_device.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/test/gmock.h"
 #include "webrtc/test/gtest.h"
 #include "webrtc/voice_engine/transmit_mixer.h"
 
 namespace webrtc {
 namespace {
 
 constexpr AgcConfig kDefaultAgcConfig = { 3, 9, true };
 
 struct TestHelper {
   TestHelper() {
+    // Reply with a 10ms timer every time TimeUntilNextProcess is called to
+    // avoid entering a tight loop on the process thread.
+    EXPECT_CALL(mock_audio_device_, TimeUntilNextProcess())
+        .WillRepeatedly(testing::Return(10));
+
     // This replicates the conditions from voe_auto_test.
     Config config;
     config.Set<ExperimentalAgc>(new ExperimentalAgc(false));
     EXPECT_EQ(0, voe_wrapper_.base()->Init(
         &mock_audio_device_,
         AudioProcessing::Create(config),
         MockAudioDecoderFactory::CreateEmptyFactory()));
   }
 
   AudioProcessing* apm() {
@@ skipping 236 matching lines @@
 // TODO(solenberg): Move this test to a better place - added here for the sake
 // of duplicating all relevant tests from audio_processing_test.cc.
 TEST(ApmHelpersTest, StereoSwapping_EnableDisable) {
   TestHelper helper;
   helper.transmit_mixer()->EnableStereoChannelSwapping(true);
   EXPECT_TRUE(helper.transmit_mixer()->IsStereoChannelSwappingEnabled());
   helper.transmit_mixer()->EnableStereoChannelSwapping(false);
   EXPECT_FALSE(helper.transmit_mixer()->IsStereoChannelSwappingEnabled());
 }
 }  // namespace webrtc