provide option to change relative URL to absolute URL in polymer build

[sigmundch]

Provide an option to allow changing relative package/ URLs (derived from HTML imports, CSS, and images) to absolute URLs after invoking pub-build.

Because this might require changing also libraries that are included transitively, this is blocked by first being able to do a global transformation.

[DartBot]

This comment was originally written by davenoti...@gmail.com

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A related discussion: https://groups.google.com/a/dartlang.org/d/msg/web/szLsH84BpQo/e1xqspqZbBsJ

[DartBot]

This issue has been moved to dart-archive/polymer-dart#432.