Create fuzzer tests for audio decoders

This change adds fuzzer tests for iLBC, iSAC fix and float, and
Opus. The fuzzer function takes a random input vector and splits it
into a number of payloads. The lengths of the payloads is also
determined by the random vector. The payloads are decoded with the
decoders.

BUG=webrtc:5306
R=kjellander@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1499093002 .

Cr-Commit-Position: refs/heads/master@{#10932}

webrtc/test/fuzzers/audio_decoder_opus_fuzzer.cc

@@ -0,0 +1,23 @@
+/*
+ *  Copyright (c) 2015 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/modules/audio_coding/codecs/opus/audio_decoder_opus.h"
+#include "webrtc/test/fuzzers/audio_decoder_fuzzer.h"
+
+namespace webrtc {
+void FuzzOneInput(const uint8_t* data, size_t size) {
+  const size_t channels = (size % 2) + 1;  // 1 or 2 channels.
+  AudioDecoderOpus dec(channels);
+  const int kSampleRateHz = 48000;
+  const size_t kAllocatedOuputSizeSamples = kSampleRateHz / 10;  // 100 ms.
+  int16_t output[kAllocatedOuputSizeSamples];
+  FuzzAudioDecoder(data, size, &dec, kSampleRateHz, sizeof(output), output);
+}
+}  // namespace webrtc