Replace remaining gflags usages with rtc_base/flags

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("../../webrtc.gni")
 
@@ skipping 331 matching lines @@
       ":webrtc_vp8",
       "../..:webrtc_common",
       "../../rtc_base:rtc_base_approved",
       "../../system_wrappers:field_trial_default",
       "../../system_wrappers:metrics_default",
       "../../system_wrappers:system_wrappers",
       "../../test:test_support",
       "../../test:video_test_common",
       "../../test:video_test_support",
       "../video_capture",
-      "//third_party/gflags",
     ]
   }  # video_quality_measurement
 
   rtc_source_set("video_codecs_test_framework") {
     testonly = true
     sources = [
       "codecs/test/mock/mock_packet_manipulator.h",
       "codecs/test/packet_manipulator.cc",
       "codecs/test/packet_manipulator.h",
       "codecs/test/predictive_packet_manipulator.cc",
@@ skipping 274 matching lines @@
     }
 
     # 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" ]
     }
   }
 }