Reapply the expanded names with the correct form of requestFileSystem on the

Reapply the expanded names with the correct form of requestFileSystem on the
test.


BUG=

Committed: https://code.google.com/p/dart/source/detail?r=20136

[Emily Fortuna, 2013-03-16 00:59:39]

Reapplying https://codereview.chromium.org//12531013
There are two differences: 
- modified mutationobserver_test.dart (I changed the syntax for specifying
options, so two of the test cases are no longer needed (the test case below
tests the same thing but in the only format available now)

- lines 25 and 35 on fileapi_test.dart This CL changes the signature of
requestFileSystem. For some reason on my local machine I had just the perfect
combination of building + testing such that this didn't run on my local checkout
when I tested it. Fixed.

[blois, 2013-03-16 01:01:18]

lgtm

[Emily Fortuna, 2013-03-16 01:02:39]

Committed patchset #1 manually as r20136 (presubmit successful).