Rename content_extractor.cc to content_extractor_browsertest.cc

Rename content_extractor.cc to content_extractor_browsertest.cc

As requested by Colin in https://codereview.chromium.org/900223003/diff/1/components/dom_distiller/standalone/content_extractor.cc#newcode1

BUG=456886
Committed: https://crrev.com/9542ef275a1f964e9e708c7e993ea0c429a91896
Cr-Commit-Position: refs/heads/master@{#315912}

[qi1988.yang, 2015-02-11 09:58:07]

qi1988.yang@samsung.com changed reviewers:
+ cjhopman@chromium.org

[qi1988.yang, 2015-02-11 09:58:08]

PTAL! Thanks!

[cjhopman, 2015-02-12 01:17:59]

lgtm

[qi1988.yang, 2015-02-12 01:52:57]

The CQ bit was checked by qi1988.yang@samsung.com

[commit-bot: I haz the power, 2015-02-12 01:54:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/917663002/1

[commit-bot: I haz the power, 2015-02-12 02:22:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 02:22:50]

Patchset 1 (id:??) landed as
https://crrev.com/9542ef275a1f964e9e708c7e993ea0c429a91896
Cr-Commit-Position: refs/heads/master@{#315912}