Implement CPU feature detection for ARM Linux.

webrtc/system_wrappers/system_wrappers.gyp

 # Copyright (c) 2012 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.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 105 matching lines @@
         }, {  # OS!="android"
           'sources!': [
             'include/logcat_trace_context.h',
             'source/logcat_trace_context.cc',
           ],
         }],
         ['OS=="linux"', {
           'defines': [
             'WEBRTC_THREAD_RR',
           ],
+          'dependencies': [
+            'cpu_features_webrtc.gyp:cpu_features_linux',

[kjellander_webrtc, 2016/03/30 19:11:17]

I'm not sure if this will compile fine with Chromium.
Would it be possible for you to create a Chromium checkout and compile Chromium
for regular Linux x86 and Linux ARM with this patch applied to
src/third_party/webrtc?
Notice you'll have to cut away one directory level when applying a patch into
that location since it's only mapping the webrtc/ subdirectory of the standalone
WebRTC repo.

+          ],
           'link_settings': {
             'libraries': [ '-lrt', ],
           },
         }],
         ['OS=="mac"', {
           'link_settings': {
             'libraries': [ '$(SDKROOT)/System/Library/Frameworks/ApplicationServices.framework', ],
           },
           'sources!': [
             'source/atomic32_posix.cc',
@@ skipping 47 matching lines @@
       'type': 'static_library',
       'dependencies': [
         'system_wrappers',
         'field_trial_default',
         'metrics_default',
       ]
     },
   ], # targets
 }