Remove system_wrappers dep from field_trial_default and metrics_default.

webrtc/system_wrappers/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/android/config.gni")
 import("../build/webrtc.gni")
 
 static_library("system_wrappers") {
   sources = [
     "interface/aligned_array.h",
     "interface/aligned_malloc.h",
     "interface/atomic32.h",
     "interface/clock.h",
     "interface/condition_variable_wrapper.h",
     "interface/cpu_features_wrapper.h",
     "interface/cpu_info.h",
     "interface/critical_section_wrapper.h",
     "interface/data_log.h",
     "interface/data_log_c.h",
     "interface/data_log_impl.h",
     "interface/event_tracer.h",
     "interface/event_wrapper.h",
     "interface/field_trial.h",

[kjellander_webrtc, 2015/10/28 13:48:43]

Not that it actually matters to the build, but wouldn't it be nicer to move this
file into the field_trial_default target if you're removing the dependency on
system_wrappers?
(since it's included in field_trial_default.cc)

[Sergey Ulanov, 2015/10/30 22:57:15]

I think this file should stay in system_wrappers as it defines functions to be
used in other parts of webrtc. 

As I discussed with Guo-wei we can avoid compile-time dependencies on external
functions like this and replace these with runtime dependency injection. So
field_trial_default and metrics_default can be removed in the future..

     "interface/file_wrapper.h",
     "interface/fix_interlocked_exchange_pointer_win.h",
     "interface/logging.h",
     "interface/metrics.h",
     "interface/ref_count.h",
     "interface/rtp_to_ntp.h",
     "interface/rw_lock_wrapper.h",
     "interface/scoped_vector.h",
     "interface/sleep.h",
     "interface/sort.h",
@@ skipping 134 matching lines @@
 }
 
 source_set("field_trial_default") {
   sources = [
     "interface/field_trial_default.h",
     "source/field_trial_default.cc",
   ]
 
   configs += [ "..:common_config" ]
   public_configs = [ "..:common_inherited_config" ]
-
-  deps = [
-    ":system_wrappers",
-  ]
 }
 
 source_set("metrics_default") {
   sources = [
     "source/metrics_default.cc",
   ]
 
   configs += [ "..:common_config" ]
   public_configs = [ "..:common_inherited_config" ]
-
-  deps = [
-    ":system_wrappers",
-  ]
 }
 
 source_set("system_wrappers_default") {
   configs += [ "..:common_config" ]
   public_configs = [ "..:common_inherited_config" ]
 
   deps = [
+    ":system_wrappers_default",

[guoweis_webrtc, 2015/10/27 23:08:07]

IS this right? Shouldn't this be system_wrappers? 

[Sergey Ulanov, 2015/10/28 00:18:42]

Yes, thanks for catching it

     ":field_trial_default",
     ":metrics_default",
   ]
 }
 
 if (is_android) {
   source_set("cpu_features_android") {
     sources = [
       "source/cpu_features_android.c",
     ]
 
     configs += [ "..:common_config" ]
     public_configs = [ "..:common_inherited_config" ]
     deps = [
       "//third_party/android_tools:cpu_features",
     ]
   }
 }