Replace EntryArray type by an Entry[]

Replace EntryArray type by an Entry[] to match the specification:
http://www.w3.org/TR/file-system-api/#the-entriescallback-interface

As a consequence, regular JavaScript Array methods can now be used.
There is no longer an item() method exposed but developers usually
access items using [] operator.

EntryArraySync is not converted to an EntrySync[] in this patch
to reduce patch size. It should be converted in a follow-up patch.

BUG=268356
R=arv@chromium.org, haraken@chromium.org, kinuko@chromium.org, tkent@chromium.org

Review URL: https://codereview.chromium.org/22436002

git-svn-id: svn://svn.chromium.org/blink/trunk@155749 bbb929c8-8fbe-4397-9dbb-9b2b20218538