Use of base::StringPairs appropriately in base

Use of base::StringPairs appropriately in base

Because base/strings/string_split.h defines:
typedef std::vector<std::pair<std::string, std::string> > StringPairs;

BUG=412250
Committed: https://crrev.com/484fbc456f3e1194708a07a315332ef0454b280a
Cr-Commit-Position: refs/heads/master@{#327129}

[packland, 2015-04-25 21:31:59]

patrikackland@gmail.com changed reviewers:
+ thestig@chromium.org

[packland, 2015-04-25 21:37:06]

Please have a look at my fix, thank you.

[Lei Zhang, 2015-04-27 20:11:38]

The CQ bit was checked by thestig@chromium.org

[Lei Zhang, 2015-04-27 20:11:39]

lgtm

[commit-bot: I haz the power, 2015-04-27 20:11:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1104693003/1

[commit-bot: I haz the power, 2015-04-27 21:29:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-27 21:30:54]

Patchset 1 (id:??) landed as
https://crrev.com/484fbc456f3e1194708a07a315332ef0454b280a
Cr-Commit-Position: refs/heads/master@{#327129}