Temporarily checkout unittest under dart/pkg/ to get the bots green until the next dartium integration is over

BUG=
R=jacobr@google.com

Review URL: https://codereview.chromium.org//816453006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42548 260f80e4-7a28-3924-810f-c04153c831b5
Fix broken reference to observe_rev

R=nweiz
BUG=

Review URL: https://codereview.chromium.org//822753002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42549 260f80e4-7a28-3924-810f-c04153c831b5
Fix a couple type bugs in dart html and what seems like strange type choices in dart:core

BUG=
R=vsm@google.com

Review URL: https://codereview.chromium.org//794953002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42550 260f80e4-7a28-3924-810f-c04153c831b5
Skip tests for `unittest` in dartium. These tests are now covered by the package bots and are not meant to be executed in the Dart bots anymore.

Note that once we fix issue 21949, these tests are not going to be run anyways (tests in
third_party/pkg/ are not executed by the Dart bots). So we can delete this line once we fix that bug.

BUG=

Review URL: https://codereview.chromium.org//819913003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42551 260f80e4-7a28-3924-810f-c04153c831b5
Fix circular dependency between null equality and identity.

R=kmillikin@google.com

Review URL: https://codereview.chromium.org//804993005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42552 260f80e4-7a28-3924-810f-c04153c831b5
Fix error in grammar for assignableExpression

Review URL: https://codereview.chromium.org//817723003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42553 260f80e4-7a28-3924-810f-c04153c831b5