Cleanup: Pass std::string as const reference from extensions/

Cleanup: Pass std::string as const reference from extensions/

Passing std::string by reference can prevent extra copying of object.

BUG=367418
TEST=
R=reillyg@chromium.org,asargent@chromium.org

Committed: https://crrev.com/4fc405185a586d3caaa51ea0d1e74ce2d8eb3b0b
Cr-Commit-Position: refs/heads/master@{#349905}

[Reilly Grant (use Gerrit), 2015-09-21 06:08:02]

lgtm

[ki.stfu, 2015-09-21 06:17:21]

The CQ bit was checked by ki.stfu@gmail.com

[commit-bot: I haz the power, 2015-09-21 06:17:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1340413004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1340413004/1

[commit-bot: I haz the power, 2015-09-21 06:55:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-21 06:55:49]

Patchset 1 (id:??) landed as
https://crrev.com/4fc405185a586d3caaa51ea0d1e74ce2d8eb3b0b
Cr-Commit-Position: refs/heads/master@{#349905}

[asargent_no_longer_on_chrome, 2015-09-21 18:20:28]

Hi ki.stfu - thanks for contributing this patch. FYI, you should only add one
reviewer to your codereview where possible, and if you need to add multiple
reviewers because some files are covered by different OWNERS files you should
explicitly state in the initial publish email who should review what. E.g. if
you needed reviews from both abcd@chromium.org and efgh@chromium.org, you'd
write something like:

abcd: please review changed files in foo/bar/baz/
efgh: please review some/file.cc

In the case of this patch reillyg and I are both in the extensions/OWNERS file,
so you only needed to add one of us. No problem; just try and remember this
guideline for the future. Thanks again for contributing!

[ki.stfu, 2015-09-21 21:18:52]

On 2015/09/21 18:20:28, Antony Sargent wrote:
> Hi ki.stfu - thanks for contributing this patch. FYI, you should only add one
> reviewer to your codereview where possible, and if you need to add multiple
> reviewers because some files are covered by different OWNERS files you should
> explicitly state in the initial publish email who should review what. E.g. if
> you needed reviews from both mailto:abcd@chromium.org and
mailto:efgh@chromium.org, you'd
> write something like:
> 
> abcd: please review changed files in foo/bar/baz/
> efgh: please review some/file.cc
> 
> In the case of this patch reillyg and I are both in the extensions/OWNERS
file,
> so you only needed to add one of us. No problem; just try and remember this
> guideline for the future. Thanks again for contributing!

@asargent: OK, thanks for clarifying!