Add linux_chromium_headless_dbg trybot builder and slaves

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

Index: masters/master.tryserver.chromium.linux/master.cfg
diff --git a/masters/master.tryserver.chromium.linux/master.cfg b/masters/master.tryserver.chromium.linux/master.cfg
index fd6f97c7c968f8505d40cb3ca8169cdfacab38e6..eaf6f232743a884868f6d12f46c5f5bce19a79a0 100644
--- a/masters/master.tryserver.chromium.linux/master.cfg
+++ b/masters/master.tryserver.chromium.linux/master.cfg
@@ -229,6 +229,14 @@ chromium_builders.extend([{
   },
 ])
 
+chromium_builders.extend([{
+    'name': 'linux_chromium_headless_dbg',
+    'factory': m_remote_run_chromium_src(
+        'chromium_trybot', max_time=master_utils.CQ_MAX_TIME),
+    'slavebuilddir': 'remote_run',
+  },
+])
+
 b_linux_site_isolation = {
   'name': 'linux_site_isolation',
   'factory': m_remote_run_chromium_src('chromium_trybot'),