Add CompareSpdyHeaderBlocks() test helper method.

Add CompareSpdyHeaderBlocks() test helper method.

Add CompareSpdyHeaderBlocks() test helper method and use in tests instead of
operator==().  This is in preparation for SpdyHeaderBlock becoming a
LinkedHashMap which does not have operator== defined.

No behavior change.

This CL lands server change 99406076 by rjshade.

BUG=443287
Committed: https://crrev.com/f29d63044b606b5e4236145e3e58ce709925eb21
Cr-Commit-Position: refs/heads/master@{#342201}

[Bence, 2015-08-05 15:03:26]

bnc@chromium.org changed reviewers:
+ rch@chromium.org

[Bence, 2015-08-05 15:03:26]

Ryan: veuillez jeter un coup d'œil s'il vous plaît.  Merci beaucoup.

[Ryan Hamilton, 2015-08-06 19:15:49]

lgtm

[Bence, 2015-08-06 19:49:25]

The CQ bit was checked by bnc@chromium.org

[commit-bot: I haz the power, 2015-08-06 19:50:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1273743002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1273743002/1

[commit-bot: I haz the power, 2015-08-06 21:34:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-06 21:34:50]

Patchset 1 (id:??) landed as
https://crrev.com/f29d63044b606b5e4236145e3e58ce709925eb21
Cr-Commit-Position: refs/heads/master@{#342201}