Break out WebAudio suspension code into new class. Add tests.

content/test/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
@@ skipping 1298 matching lines @@
     "../renderer/media/audio_renderer_mixer_manager_unittest.cc",
     "../renderer/media/audio_renderer_sink_cache_unittest.cc",
     "../renderer/media/midi_message_filter_unittest.cc",
     "../renderer/media/mock_audio_device_factory.cc",
     "../renderer/media/mock_audio_device_factory.h",
     "../renderer/media/render_media_client_unittest.cc",
     "../renderer/media/render_media_log_unittest.cc",
     "../renderer/media/video_capture_impl_manager_unittest.cc",
     "../renderer/media/video_capture_impl_unittest.cc",
     "../renderer/media/video_capture_message_filter_unittest.cc",
+    "../renderer/media/webaudio_suspender_unittest.cc",
     "../renderer/media/webmediaplayer_ms_unittest.cc",
     "../renderer/peripheral_content_heuristic_unittest.cc",
     "../renderer/render_thread_impl_unittest.cc",
     "../renderer/render_widget_unittest.cc",
     "../renderer/scheduler/resource_dispatch_throttler_unittest.cc",
     "../renderer/screen_orientation/screen_orientation_dispatcher_unittest.cc",
     "../renderer/skia_benchmarking_extension_unittest.cc",
     "fileapi_test_file_set.cc",
     "fileapi_test_file_set.h",
     "image_decoder_test.cc",
@@ skipping 360 matching lines @@
   if (is_android) {
     deps += [ "//testing/android/native_test:native_test_native_code" ]
   }
 }
 
 group("fuzzers") {
   deps = [
     "//content/test/fuzzer",
   ]
 }