diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index c5ab248175..91d14d0602 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -259,24 +259,16 @@
         'defines': [
           'WEBRTC_MAC',
           'WEBRTC_IOS',
-          'WEBRTC_THREAD_RR',
-          'WEBRTC_CLOCK_TYPE_REALTIME',
         ],
       }],
       ['OS=="linux"', {
         'defines': [
           'WEBRTC_LINUX',
-          'WEBRTC_THREAD_RR',
-          # TODO(andrew): can we select this automatically?
-          # Define this if the Linux system does not support CLOCK_MONOTONIC.
-          #'WEBRTC_CLOCK_TYPE_REALTIME',
         ],
       }],
       ['OS=="mac"', {
         'defines': [
           'WEBRTC_MAC',
-          'WEBRTC_THREAD_RR',
-          'WEBRTC_CLOCK_TYPE_REALTIME',
         ],
       }],
       ['OS=="win"', {
@@ -297,12 +289,6 @@
         'defines': [
           'WEBRTC_LINUX',
           'WEBRTC_ANDROID',
-          # TODO(leozwang): Investigate CLOCK_REALTIME and CLOCK_MONOTONIC
-          # support on Android. Keep WEBRTC_CLOCK_TYPE_REALTIME for now,
-          # remove it after I verify that CLOCK_MONOTONIC is fully functional
-          # with condition and event functions in system_wrappers.
-          'WEBRTC_CLOCK_TYPE_REALTIME',
-          'WEBRTC_THREAD_RR',
          ],
          'conditions': [
            ['enable_android_opensl==1', {
diff --git a/webrtc/system_wrappers/source/system_wrappers.gyp b/webrtc/system_wrappers/source/system_wrappers.gyp
index 8bc947b40c..36e003dbde 100644
--- a/webrtc/system_wrappers/source/system_wrappers.gyp
+++ b/webrtc/system_wrappers/source/system_wrappers.gyp
@@ -133,9 +133,23 @@
           ],
         }],
         ['OS=="android"', {
+          'defines': [
+            'WEBRTC_THREAD_RR',
+            # TODO(leozwang): Investigate CLOCK_REALTIME and CLOCK_MONOTONIC
+            # support on Android. Keep WEBRTC_CLOCK_TYPE_REALTIME for now,
+            # remove it after I verify that CLOCK_MONOTONIC is fully functional
+            # with condition and event functions in system_wrappers.
+            'WEBRTC_CLOCK_TYPE_REALTIME',
+           ],
           'dependencies': [ 'cpu_features_android', ],
         }],
         ['OS=="linux"', {
+          'defines': [
+            'WEBRTC_THREAD_RR',
+            # TODO(andrew): can we select this automatically?
+            # Define this if the Linux system does not support CLOCK_MONOTONIC.
+            #'WEBRTC_CLOCK_TYPE_REALTIME',
+          ],
           'link_settings': {
             'libraries': [ '-lrt', ],
           },
@@ -148,6 +162,12 @@
             'atomic32_posix.cc',
           ],
         }],
+        ['OS=="ios" or OS=="mac"', {
+          'defines': [
+            'WEBRTC_THREAD_RR',
+            'WEBRTC_CLOCK_TYPE_REALTIME',
+          ],
+        }],
         ['OS=="win"', {
           'link_settings': {
             'libraries': [ '-lwinmm.lib', ],