Add config for Linux layout test try bot with --enable-slimming-paint-v2.

masters/master.tryserver.chromium.linux/slaves.cfg

 # -*- python -*-
 # ex: set syntax=python:
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # See master.experimental/slaves.cfg for documentation.
 
 def linux():
   chromeos_boards = ('x86-generic', 'amd64-generic', 'daisy')
@@ skipping 155 matching lines @@
       'master': 'TryServerChromiumLinux',
       'os': 'linux',
       'version': 'precise',
       'bits': '64',
       'builder': ['linux_chromium_browser_side_navigation_rel'],
       'hostname': 'slave914-c4',
       'pool': 'linux_chromium_browser_side_navigation_rel',
     }
   ])
 
+  result.extend([
+    {
+      'master': 'TryServerChromiumLinux',
+      'os': 'linux',
+      'version': 'precise',
+      'bits': '64',
+      'builder': ['linux_layout_tests_slimming_paint_v2'],
+      'hostname': 'slave775-c4',
+      'pool': 'linux_layout_tests_slimming_paint_v2',
+    }
+  ])
+
   return result
 
 
 slaves = linux()