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

content/renderer/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/features.gni")
 import("//build/config/ui.gni")
 import("//media/media_options.gni")
 import("//third_party/webrtc/build/webrtc.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
 
@@ skipping 242 matching lines @@
     "media/renderer_webmidiaccessor_impl.cc",
     "media/renderer_webmidiaccessor_impl.h",
     "media/video_capture_impl.cc",
     "media/video_capture_impl.h",
     "media/video_capture_impl_manager.cc",
     "media/video_capture_impl_manager.h",
     "media/video_capture_message_filter.cc",
     "media/video_capture_message_filter.h",
     "media/web_media_element_source_utils.cc",
     "media/web_media_element_source_utils.h",
+    "media/webaudio_suspender.cc",
+    "media/webaudio_suspender.h",
     "media/webmediaplayer_ms.cc",
     "media/webmediaplayer_ms.h",
     "media/webmediaplayer_ms_compositor.cc",
     "media/webmediaplayer_ms_compositor.h",
     "menu_item_builder.cc",
     "menu_item_builder.h",
     "mojo/blink_interface_provider_impl.cc",
     "mojo/blink_interface_provider_impl.h",
     "mojo/interface_provider_js_wrapper.cc",
     "mojo/interface_provider_js_wrapper.h",
@@ skipping 638 matching lines @@
     # For the defines in mojo_media_config.
     public_configs = [ "//media/mojo/services:mojo_media_config" ]
   }
 
   if (!is_component_build) {
     public_deps = [
       ":renderer",
     ]
   }
 }