Replace remaining gflags usages with rtc_base/flags

webrtc/modules/remote_bitrate_estimator/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 207 matching lines @@
       "bwe_simulations.cc",
     ]
     deps = [
       ":bwe_simulator_lib",
       ":remote_bitrate_estimator",
       "../..:webrtc_common",
       "../../rtc_base:rtc_base_approved",
       "../../test:test_main",
       "//testing/gmock",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
 
     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" ]
     }
 
     if (is_win) {
       cflags = [
         # TODO(kjellander): bugs.webrtc.org/261: Fix this warning.
         "/wd4373",  # virtual function override.
       ]
     }
   }
 }