If a Dart file does an import that is 'strange', this flag
allows the imported URI to be understood by the analyzer
so long as an explicit mapping of the URI to an absolute
path to a .dart file is supplied with this flag.
For example, a custom embedding of the Dart VM may refer
to non-SDK libraries through its own URI scheme, e.g.
import 'strange:things';
With the flag and Uri resolver added in this CL, the
analyzer can find the Dart source for 'strange:things':
dartanalyzer ... --url_mapping 'strange:things,/path/to/strange/things.dart'
R=brianwilkerson@google.com
Review URL: https://codereview.chromium.org//897593005
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@43788 260f80e4-7a28-3924-810f-c04153c831b5
zra@google.com
74245deeac