Use of base::StringPairs appropriately in simple_backend_impl

Use of base::StringPairs appropriately in simple_backend_impl

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

BUG=412250
Committed: https://crrev.com/cca651ab3b8bdc2d729c34f9dd3988abd53ca81c
Cr-Commit-Position: refs/heads/master@{#327686}

[payal.pandey, 2015-04-29 10:01:22]

payal.pandey@samsung.com changed reviewers:
+ eroman@chromium.org

[payal.pandey, 2015-04-29 10:01:23]

Please have a look, Thanks.

[payal.pandey, 2015-04-29 18:58:16]

payal.pandey@samsung.com changed reviewers:
+ pasko@chromium.org

[eroman, 2015-04-29 19:32:15]

lgtm

[payal.pandey, 2015-04-30 06:31:54]

The CQ bit was checked by payal.pandey@samsung.com

[commit-bot: I haz the power, 2015-04-30 06:33:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1111203002/1

[payal.pandey, 2015-04-30 09:03:13]

The CQ bit was unchecked by payal.pandey@samsung.com

[payal.pandey, 2015-04-30 09:03:18]

The CQ bit was checked by payal.pandey@samsung.com

[commit-bot: I haz the power, 2015-04-30 09:04:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1111203002/1

[commit-bot: I haz the power, 2015-04-30 09:14:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-30 09:14:57]

Patchset 1 (id:??) landed as
https://crrev.com/cca651ab3b8bdc2d729c34f9dd3988abd53ca81c
Cr-Commit-Position: refs/heads/master@{#327686}

[pasko, 2015-04-30 09:29:27]

lgtm