Implement CPU feature detection for ARM Linux.

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")
@@ skipping 90 matching lines @@
     defines += [ "WEBRTC_THREAD_RR" ]
 
     deps += [ ":cpu_features_android" ]
 
     libs += [ "log" ]
   }
 
   if (is_linux) {
     defines += [ "WEBRTC_THREAD_RR" ]
 
+    deps += [ ":cpu_features_linux" ]

[kjellander_webrtc, 2016/04/04 06:09:45]

Please introduce the similar if (build_with_chromium) condition here as for the
GYP build.

[Simon Hosie, 2016/04/05 01:15:48]

Done.

+
     libs += [ "rt" ]
   }
 
   if (!is_mac && !is_ios) {
     sources += [ "source/atomic32_posix.cc" ]
   }
 
   if (is_ios || is_mac) {
     defines += [ "WEBRTC_THREAD_RR" ]
   }
@@ skipping 50 matching lines @@
       "source/cpu_features_android.c",
     ]
 
     configs += [ "..:common_config" ]
     public_configs = [ "..:common_inherited_config" ]
     deps = [
       "//third_party/android_tools:cpu_features",
     ]
   }
 }
+
+if (is_linux) {
+  source_set("cpu_features_linux") {
+    sources = [
+      "source/cpu_features_linux.c",
+    ]
+
+    configs += [ "..:common_config" ]
+    public_configs = [ "..:common_inherited_config" ]
+  }
+}