Reland of Moving webrtc.gni up one level from build/

webrtc/modules/rtp_rtcp/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")
+import("../../webrtc.gni")
 
 rtc_static_library("rtp_rtcp") {
   sources = [
     "include/flexfec_receiver.h",
     "include/flexfec_sender.h",
     "include/receive_statistics.h",
     "include/remote_ntp_time_estimator.h",
     "include/rtp_header_parser.h",
     "include/rtp_payload_registry.h",
     "include/rtp_receiver.h",
@@ skipping 273 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" ]
     }
   }
 }