Share a body across all versions of a message.

Share a body across all versions of a message.

This means that when one message is read, all other messages that were
created from the same original via `change()` will be marked read as
well.

Closes #49

R=rnystrom@google.com

Committed: https://github.com/dart-lang/shelf/commit/5bab305148a4064069c950ad3838cc622a1d570e

[nweiz, 2015-08-31 19:59:30]

nweiz@google.com changed reviewers:
+ rnystrom@google.com

[Bob Nystrom, 2015-08-31 21:05:33]

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart
File lib/src/body.dart (right):

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode22
lib/src/body.dart:22: bool _wasRead = false;
How about just making _stream writable, and setting it to null after it's read?

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode34
lib/src/body.dart:34: if (body is Body) return body;
This means doing new Body(previouslyReadBody) doesn't give you something
readable. Is that OK?

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode35
lib/src/body.dart:35: 
Should this throw if an encoding is prodivided but body is a type where it will
never be used?

[nweiz, 2015-08-31 21:16:00]

Code review changes

[nweiz, 2015-08-31 21:16:05]

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart
File lib/src/body.dart (right):

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode22
lib/src/body.dart:22: bool _wasRead = false;
On 2015/08/31 21:05:32, Bob Nystrom wrote:
> How about just making _stream writable, and setting it to null after it's
read?

Done.

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode34
lib/src/body.dart:34: if (body is Body) return body;
On 2015/08/31 21:05:32, Bob Nystrom wrote:
> This means doing new Body(previouslyReadBody) doesn't give you something
> readable. Is that OK?

Yeah, I think that matches the expected semantics of `change()`.

https://codereview.chromium.org/1327453002/diff/1/lib/src/body.dart#newcode35
lib/src/body.dart:35: 
On 2015/08/31 21:05:32, Bob Nystrom wrote:
> Should this throw if an encoding is prodivided but body is a type where it
will
> never be used?

I think  it's probably fine. Definitely not worth a backwards-incompatible
change.

[Bob Nystrom, 2015-08-31 21:31:19]

lgtm

[nweiz, 2015-09-01 02:01:44]

Committed patchset #2 (id:20001) manually as
5bab305148a4064069c950ad3838cc622a1d570e (presubmit successful).