WebRTC: Reshuffle Mac trybot slaves.

masters/master.tryserver.webrtc/slaves.cfg

Index: masters/master.tryserver.webrtc/slaves.cfg
diff --git a/masters/master.tryserver.webrtc/slaves.cfg b/masters/master.tryserver.webrtc/slaves.cfg
index fe5dcc9a16eb75a0db8c197a35a96a500cb8722e..7170850fa2638d779aa7e8b6642ee89e16cbe007 100644
--- a/masters/master.tryserver.webrtc/slaves.cfg
+++ b/masters/master.tryserver.webrtc/slaves.cfg
@@ -99,17 +99,26 @@ slaves = [
       'mac',
       'mac_rel',
       'mac_x64_rel',
-      'mac_x64_gn',
-      'mac_x64_gn_rel',
-      'mac_asan',
       'ios',
       'ios_rel',
       'ios_arm64',
       'ios_arm64_rel',
     ],
     'hostname': 'vm%d-m4' % i,
-  } for i in range(738, 741) + range(818, 820)
+  } for i in range(738, 741) + [818]
 ] + [
+  {
+    'master': 'WebRTCTryServer',
+    'os': 'mac',
+    'version': '10.8',
+    'bits': '64',
+    'builder': [
+      'mac_asan',
+      'mac_x64_gn',
+      'mac_x64_gn_rel',
+    ],
+    'hostname': 'vm819-m4',
+  },
   # Mac bare-metal machines with audio devices and headsets.
   {
     'master': 'WebRTCTryServer',