Ember.isArray return true for FileList object

[joelcox]

Passing a FileList object to Ember.isArray returns true, even though it does not behave like an Ember Array/Enumerable. I'm not sure if this is within the scope of Ember.

JSBin: http://emberjs.jsbin.com/ricokobotu/8/edit?js,console,output

Interesting bit from the File spec:

The FileList interface should be considered "at risk" since the general trend on the Web Platform is to replace such interfaces with the Array platform object in ECMAScript [ECMA-262]. In particular, this means syntax of the sort filelist.item(0) is at risk; most other programmatic use of FileList is unlikely to be affected by the eventual migration to an Array type.

[pixelhandler]

@joelcox yeah seems like Ember.isArray() has a bug; using Array.isArray(files) is false. Perhaps avoid Ember.isArray() for now.

[mmun]

We should fix this bug. Ember.isArray is useful because it can be used to detect an ArrayProxy, whereas Array.isArray cannot.

[joelalejandro]

@mmun There was a fix apparently, but it didn't pass CI for IE9, for what I read in referenced PRs.

[mixonic]

The approach in #12708 seems quite legit