Create a mechanism define declarative rules via the extension manifest.

extensions/common/api/events.json

Index: extensions/common/api/events.json
diff --git a/extensions/common/api/events.json b/extensions/common/api/events.json
index e62ea09c68e4a7542b51202de0d59f6dd3af941f..1e830d2d2a42304f91d59d0e8c0f92843c0a2888 100644
--- a/extensions/common/api/events.json
+++ b/extensions/common/api/events.json
@@ -20,6 +20,11 @@
             "optional": true,
             "description": "Optional identifier that allows referencing this rule."
           },
+          "removable": {

[not at google - send to devlin, 2015/06/04 17:58:49]

This shouldn't be part of the public API, instead, annotate it in the internal
data structure you use.

[danduong, 2015/06/04 19:10:59]

Which internal data-structure. Part of the reason why it is here is because how
the serialization to storage works. 

[not at google - send to devlin, 2015/06/04 19:23:53]

However rules are implemented in C++. you're changing the public API here.

[danduong, 2015/06/04 21:39:40]

Done.

+            "type": "boolean",
+            "optional": true,
+            "description":  "False if the rule is not programmatically removable."
+          },
           "tags": {
             "type": "array",
             "items": {"type": "string"},