Use std::tie() for operator< in content/

Use std::tie() for operator< in content/

Simplify the code for operator< when comparing multiple members using
a common std::tie idiom.

BUG=555171
R=jochen@chromium.org

Committed: https://crrev.com/71dafdfe7183b9b016460ceb0d1ce184b7aee341
Cr-Commit-Position: refs/heads/master@{#360883}

[jsbell, 2015-11-19 22:16:19]

jochen@ - please take a look?

[kinuko, 2015-11-20 04:24:15]

Just saw this, drive-by lgtm

[jochen (gone - plz use gerrit), 2015-11-20 13:37:50]

jochen@chromium.org changed reviewers:
+ kinuko@chromium.org

[jochen (gone - plz use gerrit), 2015-11-20 13:37:50]

lgtm

[jsbell, 2015-11-20 19:01:32]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2015-11-20 19:05:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1462213002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1462213002/1

[commit-bot: I haz the power, 2015-11-20 19:40:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-20 19:42:06]

Patchset 1 (id:??) landed as
https://crrev.com/71dafdfe7183b9b016460ceb0d1ce184b7aee341
Cr-Commit-Position: refs/heads/master@{#360883}