[Android] Set up continuous builder + trybot for cronet.

masters/master.chromium.android/builders.pyl

 {
   "master_base_class": "Master1",
   "master_port": 20101,
   "master_port_alt": 40101,
   "slave_port": 30101,
   "pubsub_service_account_file": "service-account-luci-milo.json",
   "templates": ["templates", "../master.chromium/templates"],
 
   "default_remote_run_properties": {
     "path_config": "kitchen",
   },
   "default_remote_run_repository": "https://chromium.googlesource.com/chromium/src.git",
 
   "builders": {
+    "Android Cronet Builder": {
+      "recipe": "chromium",
+      "scheduler": "android_commits",
+      "slave_pools": ["builders"],
+      "slavebuilddir": "cronet",
+      "category": "0Cronet",
+    },
     "Android Cronet KitKat Builder": {
       "recipe": "cronet",
       "scheduler": "android_commits",
       "slave_pools": ["cronet_k_hammerhead"],
       "category": "0Cronet",
     },
     "Android Cronet Lollipop Builder": {
       "recipe": "cronet",
       "scheduler": "android_commits",
       "slave_pools": ["cronet_l_hammerhead"],
@@ skipping 442 matching lines @@
     "webview_m": {
       "slave_data": {
         "os": "linux",
         "version": "trusty",
         "bits": 64,
       },
       "slaves": ["build37-b1"],
     },
   }
 }