Add a CQ tester (which will start as experimental) with N5's on L.

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 37bace30ab16e45b78fb24e5aca1166e4c98b526..c6076237d0f1299d569854d88c4aaf5fa99222b0 100644
--- a/masters/master.tryserver.chromium.linux/slaves.cfg
+++ b/masters/master.tryserver.chromium.linux/slaves.cfg
@@ -187,7 +187,7 @@ def android():
       'os': 'linux',
       'version': 'precise',
       'bits': '64',
-    } for i in range(100,139+1)
+    } for i in range(100,138+1)
   ]
 
   amp_slaves = [
@@ -212,7 +212,18 @@ def android():
     } for i in range(520, 540)
   ]
 
-  return compile_slaves + test_slaves + amp_slaves + aosp_slaves
+  n5_experiment = [
+    {
+      'master': 'TryServerChromiumLinux',
+      'builder': 'android_n5_rel_tests_recipe',
+      'hostname': 'build139-a4',
+      'os': 'linux',
+      'version': 'precise',
+      'bits': '64',
+    }
+  ]
+
+  return compile_slaves + test_slaves + amp_slaves + aosp_slaves + n5_experiment
 
 
 slaves = linux() + android()