Move AudioDecoder and AudioDecoderFactory mocks to webrtc/test/

webrtc/test/BUILD.gn

 # Copyright (c) 2014 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.
 
 import("../webrtc.gni")
 import("//build/config/ui.gni")
@@ skipping 471 matching lines @@
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     ":test_support",
     "../modules/media_file",
     "//testing/gtest",
   ]
 }
+
+rtc_source_set("audio_codec_mocks") {
+  testonly = true
+  sources = [
+    "mock_audio_decoder.h",
+    "mock_audio_decoder_factory.h",
+  ]
+}