Restructure protobuf targets to fit with downstream requirements.

webrtc/modules/audio_processing/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/config/arm.gni")
 import("//third_party/protobuf/proto_library.gni")
@@ skipping 776 matching lines @@
         "//third_party/gflags",
       ]
     }
   }
 
   if (rtc_enable_protobuf) {
     proto_library("audioproc_unittest_proto") {
       sources = [
         "test/unittest.proto",
       ]
-      proto_out_dir = "webrtc/modules/audio_processing"
+      proto_out_dir = "webrtc/modules/audio_processing/test"
     }
 
     rtc_static_library("audioproc_protobuf_utils") {
       sources = [
         "test/protobuf_utils.cc",
         "test/protobuf_utils.h",
       ]
 
       deps = [
         ":audioproc_debug_proto",
         "../..:webrtc_common",
         "../../base:rtc_base_approved",
       ]
     }
   }
 }