Add enabled flag for try builders

ci/dev/README.md

@@ -8,16 +8,25 @@ supported luci try/prod builders for engine. It follows format:
 {
     "builders":[
         {
-            "name":"xxx",
-            "repo":"engine"
-        },
+            "name":"yyy",
+            "repo":"engine",
+            "enabled":true
+        }
+    ]
+}
+```
+for `try_builders.json`, and follows format:
+```json
+{
+    "builders":[
         {
             "name":"yyy",
             "repo":"engine"
         }
     ]
 }
 ```
-This file will be mainly used in [`flutter/cocoon`](https://github.com/flutter/cocoon)
-to trigger/update engine luci tasks.
-
+for `prod_builders.json`. `try_builders.json` will be mainly used in 
+[`flutter/cocoon`](https://github.com/flutter/cocoon) to trigger/update pre-submit
+engine luci tasks, whereas `prod_builders.json` will be mainly used in `flutter/cocoon`
+to push luci task statuses to GitHub.

ci/dev/try_builders.json

@@ -2,55 +2,68 @@
    "builders":[
       {
          "name":"Linux Host Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Linux Fuchsia",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Linux Android AOT Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Linux Android Debug Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Linux Web Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Mac Host Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Mac Android AOT Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Mac Android Debug Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Mac iOS Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Windows Host Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Windows Android AOT Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Windows Web Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       },
       {
          "name":"Mac Web Engine",
-         "repo":"engine"
+         "repo":"engine",
+         "enabled": true
       }
    ]
 }