Introduce session type parameter to extension features

chrome/test/data/extensions/extension_api_unittest/api_features.json

 {
   "test1": {
     "channel": "stable",
     "contexts": ["content_script", "blessed_extension", "unblessed_extension"],
     "extension_types": ["extension"]
   },
   "test2": {
     "channel": "stable",
     "contexts": ["web_page"],
     "matches": ["<all_urls>"]
@@ skipping 73 matching lines @@
   "parent3": {
     "dependencies": ["api:parent1"],
     "contexts": ["content_script", "blessed_extension", "unblessed_extension"]
   },
   "parent3.noparent": {
     "channel": "stable",
     "noparent": true,
     "contexts": ["content_script", "blessed_extension", "unblessed_extension"]
   },
   "parent3.noparent.child": {
+  },
+  "kiosk_only": {
+    "channel": "stable",
+    "contexts": ["content_script", "blessed_extension", "unblessed_extension"],
+    "session_types": ["kiosk"]
+  },
+  "non_kiosk": {
+    "channel": "stable",
+    "contexts": ["content_script", "blessed_extension", "unblessed_extension"],
+    "session_types": ["regular"]
+  },
+  "empty_session_types": {
+    "channel": "stable",
+    "contexts": ["content_script", "blessed_extension", "unblessed_extension"],
+    "session_types": []
+  },
+  "all_session_types": {

[Devlin, 2016/08/23 20:49:06]

"all" is doomed to be obsoleted, unless it uses "all". :)

[tbarzic, 2016/09/08 18:48:55]

yeah, I agree, fixed

+    "channel": "stable",
+    "contexts": ["content_script", "blessed_extension", "unblessed_extension"],
+    "session_types": ["kiosk", "regular"]

[Devlin, 2016/08/23 20:49:06]

How would one specify "unknown"?

[tbarzic, 2016/09/08 18:48:54]

it's not possible, by design - "unknown" session type is used internally a a
value for session type against which feature session type should be matched in
order to determine feature availability (it represents a session type that
cannot be declared in "session_types" list)

   }
 }