Work around naming conflict in analyzer's Resource class.

Work around naming conflict in analyzer's Resource class.

Commit f8ce36df557af9028ef72612a43e9942d6f16585 introduced an SDK
class called "Resource", causing warnings to appear in any files that
reference the analyzer class with the same name.  (Fortunately there
was no regression in functionality since the spec requires the name
conflict to be resolved in favor of the definition that is outside the
SDK).

As a short term workaround to avoid the warnings, we are explicitly
importing 'dart:core' and hiding the new Resource class.  In a future
CL, we plan to rework analyzer's Resource class in order to make some
changes necessary for ".packages" file support; when that happens we
will probably rename the class to avoid the name conflict.

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/db6c95502a8250a036227356824527f1a4e31b23

[Paul Berry, 2015-06-26 17:57:19]

paulberry@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2015-06-26 18:35:55]

LGTM

[Paul Berry, 2015-06-26 20:00:49]

Committed patchset #1 (id:1) manually as
db6c95502a8250a036227356824527f1a4e31b23 (presubmit successful).