Reapply "Make Map constructors return LinkedHashMap."
Reapply "Make Map constructors return LinkedHashMap."

Updated tests assuming a specific ordering of an unlinked hash map
to not be daft.

R=floitsch@google.com, jmesserly@google.com

Review URL: https://codereview.chromium.org//22859069

git-svn-id: 0aa7e0b98478d6ef7145d04e8154f8ab2209deba@26693 260f80e4-7a28-3924-810f-c04153c831b5

meflyup/polymer-dart,dart-archive/polymer-dart,jakemac53/polymer-dart,dam0vm3nt/polymer-dart,dart-archive/polymer-dart,ronlobo/polymer-dart,meflyup/polymer-dart,dam0vm3nt/polymer-dart,jakemac53/polymer-dart,ronlobo/polymer-dart