Don't treat the primary input as a secondary input in barback.

Don't treat the primary input as a secondary input in barback.

Some transformers use [Transform.readInputAsString] to read their
primary input, which puts it into a weird state of being considered
both a primary and a secondary input. This ensures that it always goes
through the normal [primaryInput] path.

R=rnystrom@google.com

Committed: https://code.google.com/p/dart/source/detail?r=34905

[Bob Nystrom, 2014-04-09 18:07:47]

Does this affect any visible behavior? If so, can it be tested?

[nweiz, 2014-04-09 21:24:31]

On 2014/04/09 18:07:47, Bob Nystrom wrote:
> Does this affect any visible behavior? If so, can it be tested?

Not without a lot of contortions. Pete ran into visible behavior, but only
because he was doing cross-phase out-of-band communication between transformers.

[Bob Nystrom, 2014-04-09 23:33:09]

lgtm

[nweiz, 2014-04-09 23:51:12]

Committed patchset #1 manually as r34905 (presubmit successful).