Jonas Jenwald 62f28e11a3 [MessageHandler] Remove unnecessary usage of in from the code
Note that using `in` leads to unnecessary stringification of the properties, which seems completely unnecessary here. To avoid future problems from these changes the `MessageHandler.on` method will now assert, in non-`PRODUCTION`/`TESTING` builds, that it's always called with a function as expected.

This patch also renames `callbacksCapabilities` to `callbackCapabilities`, note the removed "s", since using a double plural format looks a bit strange.
2019-10-30 23:22:59 +01:00
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2012-10-29 14:08:52 -04:00