Let alr dectector use a budged to detect underuse.

webrtc/modules/pacing/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")
 
 rtc_static_library("pacing") {
   sources = [
     "alr_detector.cc",
     "alr_detector.h",
     "bitrate_prober.cc",
     "bitrate_prober.h",
+    "interval_budget.cc",
+    "interval_budget.h",
     "paced_sender.cc",
     "paced_sender.h",
     "packet_router.cc",
     "packet_router.h",
   ]
 
   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" ]
   }
@@ skipping 16 matching lines @@
 
     # Skip restricting visibility on mobile platforms since the tests on those
     # gets additional generated targets which would require many lines here to
     # cover (which would be confusing to read and hard to maintain).
     if (!is_android && !is_ios) {
       visibility = [ "//webrtc/modules:modules_unittests" ]
     }
     sources = [
       "alr_detector_unittest.cc",
       "bitrate_prober_unittest.cc",
+      "interval_budget_unittest.cc",
       "paced_sender_unittest.cc",
       "packet_router_unittest.cc",
     ]
     deps = [
       ":pacing",
       "../../base:rtc_base_approved",
       "../../base:rtc_base_tests_utils",
       "../../system_wrappers:system_wrappers",
       "../../test:test_support",
       "../rtp_rtcp",
       "../rtp_rtcp:mock_rtp_rtcp",
       "//testing/gmock",
     ]
 
     # TODO(jschuh): bugs.webrtc.org/1348: fix this warning.
     configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
     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" ]
     }
   }
 }