Backpatch net/http: avoid a bunch of unnecessary CanonicalHeaderKey calls

changeset:   13637:3ad9da69a1a7
parent:      13635:40dc2beda77f
user:        Brad Fitzpatrick <bradfitz@golang.org>
date:        Mon May 28 11:07:24 2012 -0700
summary:     net/http: avoid a bunch of unnecessary CanonicalHeaderKey calls

To my naive eyes, it seems like this refactoring missed completion (it
seems like .get is a fast path for all literally-provided header
names), but nevertheless faithfully complete what the patch does, no
more, and no less.

Signed-off-by: Daniel Farina <daniel@fdr.io>
Backport transport_test from tip

Right now, it doesn't pass.  I surmise this is from bugs that have
since been fixed.

Just as well: this was to prepare for backpatching fixes.

Signed-off-by: Daniel Farina <daniel@fdr.io>