WebRTC: Add Libfuzzer commit and trybot.

masters/master.client.webrtc/master_linux_cfg.py

Index: masters/master.client.webrtc/master_linux_cfg.py
diff --git a/masters/master.client.webrtc/master_linux_cfg.py b/masters/master.client.webrtc/master_linux_cfg.py
index 480f2b675fe79f1ebeb4d533dce9a437ef83a549..02f46457b25c4f54f8e4574811c2de2e6d7e2b0b 100644
--- a/masters/master.client.webrtc/master_linux_cfg.py
+++ b/masters/master.client.webrtc/master_linux_cfg.py
@@ -25,6 +25,7 @@ def Update(c):
           'Linux64 Release [large tests]',
           'Linux64 Debug (GN)',
           'Linux64 Release (GN)',
+          'Linux64 Release (Libfuzzer)',
       ]),
   ])
 
@@ -46,6 +47,10 @@ def Update(c):
     },
     {'name': 'Linux64 Debug (GN)', 'slavebuilddir': 'linux64_gn'},
     {'name': 'Linux64 Release (GN)', 'slavebuilddir': 'linux64_gn'},
+    {
+      'name': 'Linux64 Release (Libfuzzer)',
+      'slavebuilddir': 'linux64_libfuzzer',
+    },
   ]
 
   c['builders'].extend([