Extract bitrate allocation of spatial/temporal layers out of codec impl.

webrtc/modules/video_coding/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("../../build/webrtc.gni")
 
@@ skipping 78 matching lines @@
     ":webrtc_vp8",
     ":webrtc_vp9",
     "../..:webrtc_common",
     "../../common_video",
     "../../system_wrappers",
   ]
 }
 
 rtc_static_library("video_coding_utility") {
   sources = [
+    "utility/default_video_bitrate_allocator.cc",
+    "utility/default_video_bitrate_allocator.h",
     "utility/frame_dropper.cc",
     "utility/frame_dropper.h",
     "utility/h264_bitstream_parser.cc",
     "utility/h264_bitstream_parser.h",
     "utility/ivf_file_writer.cc",
     "utility/ivf_file_writer.h",
     "utility/moving_average.cc",
     "utility/moving_average.h",
     "utility/qp_parser.cc",
     "utility/qp_parser.h",
@@ skipping 213 matching lines @@
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       "../../test:test_support",
     ]
   }
 }