Using package:http carries ~100kB cost

[matanlurey]

Reproduction case @ https://github.com/matanlurey/http-browser-benchmark

Significant parts:

• Uses ~30kB more from dart:core, I assume this is use of Uri.
• Brings in package:path (~10kB).
• Brings in package:stack_trace (~8kB).
• Brings in package:source_span(~6kB).
• Brings in package:http_parser, string_scanner (~4kB combined).
• Brings in an extra ~6kB from dart:convert.

This is an issue when trying to use this package for mobile web applications. I can't see a clear reason why I need 100kB more for simple JSON requests given that we aren't using any of the other functionality.

[nex3]

I'd definitely like to get the size down as much as possible without hurting functionality. The stack_trace dependency has already been removed in #115 (on master) and #123 (on 0.11.x). I think I can get rid of the source_span and path dependencies too once dart-lang/sdk#30962 and dart-lang/sdk#30963 are fixed. I believe the code size hit from Uri will be also be vastly smaller once the changes described in dart-lang/sdk#29420 (comment) happen and the class becomes a thin shim over the browser's URL support.

[natebosch]

Closing since this is not something we plan to push on.

source_span is no longer a dependency.

path could be dropped if we re-implement basename, but that doesn't look straightforward enough to be worthwhile.

It's unlikely we'll be able to drop the dep on http_parser