Update clock dart packaged app example for a modern dart.

This change allows the clock to run in Dartium m31, or in Chrome,
without changes.

Changes:
 dart2js no longer accepts --disallow-unsafe-eval
 window.requestLayoutFrame is now scheudleMicrotask from dart:async.
 Date is now DateTime
 List<E>.filter is now List<E>.removeWhere
 String.charCodeAt is now String.codeUnitAt
 js/interop stuff no longer required

Bugfix: Fix numbers not showing up at all when first opened, e.g., at
exactly 4pm and now.minute == 0.

Review URL: https://codereview.appspot.com/56440043
Fixes indents
Added zoom and find buttons
Implemented the zoom box.
Implemented the find box.
Added matchCase functionality to the find box.
Added incremental find
Find box moves out of the way or becomes translucent
Made the find bar not obscure active matches, and some other small improvements
Added zoom in and out buttons and ctrl+f shortcut
Added keyboard shortcuts for zoom
Hides new API functionality when they are not available (e.g. experimental APIs not enabled).
Added stopFinding('activate') functionality
Cleaned up the css a bit.
Moved the find box intersection conditions to a helper method.
Merge pull request #206 from pauldylanmeyer/master

Added zoom and find-in-page functionality.
Removed incorrect window id
fixed some dead links
Merge pull request #207 from Nickdouille/patch-1

fixed some dead links
Merge pull request #201 from watilde/master

Fixes indents