Add linux_chromium_headless_dbg trybot builder and slaves

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

Index: masters/master.tryserver.chromium.linux/slaves.cfg
diff --git a/masters/master.tryserver.chromium.linux/slaves.cfg b/masters/master.tryserver.chromium.linux/slaves.cfg
index 4c796b081896542589867fa648712298146f5040..e78facf817cd54342cd4ba9c36ecc9eb66c5d38e 100644
--- a/masters/master.tryserver.chromium.linux/slaves.cfg
+++ b/masters/master.tryserver.chromium.linux/slaves.cfg
@@ -8,11 +8,11 @@
 
 def linux():
   chromeos_boards = ('x86-generic', 'amd64-generic', 'daisy')
-  cq_slaves = (range(111, 131) + range(162, 399) + range(427, 453) +
-               range(493, 497) + range(506, 540) + range(590, 600) +
-               range(621, 651) + range(779, 799) + range(800, 837) +
-               range(841, 864) + range(878, 897) + range(909, 914) +
-               range(1010, 1029))
+  cq_slaves = (range(111, 131) + range(162, 399) + range(426, 453) +
+               range(493, 498) + range(506, 540) + range(590, 600) +
+               range(621, 651) + [776] + range(779, 799) + range(800, 837) +
+               range(841, 866) + [872] + range(878, 897) + range(909, 914) +
+               range(1010, 1029) + range(1069, 1098))
   cq_builders = [
     'blimp_linux_dbg',
     'cast_shell_linux',
@@ -28,6 +28,7 @@ def linux():
     'linux_chromium_compile_dbg_ng',
     'linux_chromium_gn_chromeos_dbg',
     'linux_chromium_gn_chromeos_rel',
+    'linux_chromium_headless_dbg',
     'linux_chromium_rel_ng',
   ]
   cq_builders += [