Decompose //extensions/browser/BUILD.gn

extensions/browser/api/audio/BUILD.gn

 # Copyright 2015 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.
-
-static_library("browser") {
+source_set("audio") {
   sources = [
-    "print_manager.cc",
-    "print_manager.h",
-    "print_manager_utils.cc",
-    "print_manager_utils.h",
+    "audio_api.cc",
+    "audio_api.h",
+    "audio_service.h",
   ]
 
   deps = [
-    "//base",
-    "//components/printing/common",
     "//content/public/browser",
-    "//printing",
+    "//skia",
   ]
+
+  if (is_chromeos) {
+    sources += [ "audio_service_chromeos.cc" ]
+  } else {
+    sources += [ "audio_service.cc" ]
+  }
 }