Introduce lock screen app context to extension features

chrome/common/extensions/api/_features.md

Index: chrome/common/extensions/api/_features.md
diff --git a/chrome/common/extensions/api/_features.md b/chrome/common/extensions/api/_features.md
index b0e406ca496fca29fe02f3a2e9dab22dd689684c..853958b508779f7928ac3b7e75c39f370fcba875 100644
--- a/chrome/common/extensions/api/_features.md
+++ b/chrome/common/extensions/api/_features.md
@@ -206,7 +206,7 @@ features can specify contexts.
 
 Accepted values are a list of strings from `blessed_extension`,
 `blessed_web_page`, `content_script`, `extension_service_worker`,
-`web_page`, `webui`, and `unblessed_extension`.
+`lock_screen_extension`, `web_page`, `webui`, and `unblessed_extension`.

[Devlin, 2017/06/01 22:17:58]

will there be any other type of context on the lock screen?  I'm wondering if
this is conceptually most similar to context or something like session type.

[tbarzic, 2017/06/02 00:49:05]

I was thinking about adding it to session type, but I think it's closer to
context (as lock screen is essentially a state of regular user session).

I don't expect any other context types on lock screen (at least not something
that would be relevant for extension features) - if that expectation does not
hold, I'd consider adding a separate "setting" for this; maybe session_state:
{LOCKED, ACTIVE, NOT_STARTED}.

 
 ### default\_parent