WebRTC+libyuv: switch to use_allocator GYP variable.

masters/master.client.webrtc/master_mac_cfg.py

Index: masters/master.client.webrtc/master_mac_cfg.py
diff --git a/masters/master.client.webrtc/master_mac_cfg.py b/masters/master.client.webrtc/master_mac_cfg.py
index 1cd507aa88f70359a7f4d2d4ea122f1a31ca5f8b..5c67bbdbb621f85dd79d956815bd87145db528c9 100644
--- a/masters/master.client.webrtc/master_mac_cfg.py
+++ b/masters/master.client.webrtc/master_mac_cfg.py
@@ -102,11 +102,10 @@ F('mac_asan_factory', mac().WebRTCFactory(
     target='Release',
     options=options,
     tests=tests,
-    factory_properties={'asan': True,
-                        'gclient_env':
-                        {'GYP_DEFINES': ('asan=1'
-                                         ' release_extra_cflags=-g '
-                                         ' linux_use_tcmalloc=0 ')}}))
+    factory_properties={
+        'asan': True,
+        'gclient_env': {'GYP_DEFINES': 'asan=1 release_extra_cflags=-g'},
+    }))
 
 B('Mac32 Release [large tests]', 'mac_largetests_factory',
   'compile|baremetal', scheduler)