Fix internal constructor in context.

BUG=
R=lrn@google.com

Review URL: https://codereview.chromium.org//434393002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@38845 260f80e4-7a28-3924-810f-c04153c831b5
Add check to watcher, to avoid null-error if unknown path is removed.

BUG=
R=kevmoo@google.com

Review URL: https://codereview.chromium.org//428493004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@38846 260f80e4-7a28-3924-810f-c04153c831b5
Mix in [TreeElementMixin] only on nodes that need it.

BUG=http://dartbug.com/16002
R=floitsch@google.com

Review URL: https://codereview.chromium.org//422483002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@38847 260f80e4-7a28-3924-810f-c04153c831b5
Performance tweak on int.parse.

Slower for strings with trailing, but no leading,
whitespace, but significantly faster for strings with no whitespace,
which is presumed to be the most common case.

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

Review URL: https://codereview.chromium.org//398813002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@38848 260f80e4-7a28-3924-810f-c04153c831b5