Add fallback to load the original version of dart:io library

Add fallback to load the original version of dart:io library
if url mapping is not provided.

R=asiva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=21892

[siva, 2013-04-19 17:47:50]

https://codereview.chromium.org/14366024/diff/1/runtime/bin/gen_snapshot.cc
File runtime/bin/gen_snapshot.cc (right):

https://codereview.chromium.org/14366024/diff/1/runtime/bin/gen_snapshot.cc#n...
runtime/bin/gen_snapshot.cc:311: }
Not sure if I understand this. The comment states that if not url mapping for
dart:io. Load original version but it seems like the original version will be
loaded even when mapped_url_string is non NULL, could you elaborate a bit more.

[podivilov, 2013-04-20 07:34:21]

PTAL.

https://codereview.chromium.org/14366024/diff/1/runtime/bin/gen_snapshot.cc
File runtime/bin/gen_snapshot.cc (right):

https://codereview.chromium.org/14366024/diff/1/runtime/bin/gen_snapshot.cc#n...
runtime/bin/gen_snapshot.cc:311: }
On 2013/04/19 17:47:50, siva wrote:
> Not sure if I understand this. The comment states that if not url mapping for
> dart:io. Load original version but it seems like the original version will be
> loaded even when mapped_url_string is non NULL, could you elaborate a bit
more.

Good spot! I misinterpreted "return resolved_url" above.

[podivilov, 2013-04-23 07:36:38]

ping

[siva, 2013-04-23 16:19:09]

lgtm

[podivilov, 2013-04-23 16:26:45]

Committed patchset #2 manually as r21892 (presubmit successful).