Deprecation Guide for Reversed Ember.observer Arguments

A little known feature of the observer function allowed for the arguments to be listed in the opposite order, with function first:

Ember.observer(function() {
  // React to observer firing here
}, 'property1', 'property2')

This syntax was deprecated in Ember 1.13.5. The above code sample should be replaced with the standard syntax that lists the observed properties, then the function as the last argument:

Ember.observer('property1', 'property2', function() {
  // React to observer firing here
})