//components/variations: Create separate target for VariationsService

//components/variations: Create separate target for VariationsService

When VariationsService is componentized, it will bring in dependencies on //net
and //ui, which are unwanted in the //components/variations target. In
particular, Cronet depends on //components/variations and cannot depend on
//net.

This CL creates //components/variations/service, which currently holds
variations_service_client.h and will hold variations_service.* once it is
componentized.

BUG=516678
TBR=brettw

Committed: https://crrev.com/b50ad70d3243979e42fe667a9b9e26bd1910eba9
Cr-Commit-Position: refs/heads/master@{#345905}

[blundell, 2015-08-27 13:47:54]

blundell@chromium.org changed reviewers:
+ asvitkine@chromium.org

[Alexei Svitkine (slow), 2015-08-27 15:11:23]

lgtm

[blundell, 2015-08-27 15:25:18]

blundell@chromium.org changed reviewers:
+ brettw@chromium.org

[blundell, 2015-08-27 15:25:31]

TBR=brettw for the trival change to //chrome/browser/BUILD.gn

[blundell, 2015-08-27 15:26:29]

The CQ bit was checked by blundell@chromium.org

[commit-bot: I haz the power, 2015-08-27 15:26:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1306893007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1306893007/1

[commit-bot: I haz the power, 2015-08-27 17:08:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-27 17:09:16]

Patchset 1 (id:??) landed as
https://crrev.com/b50ad70d3243979e42fe667a9b9e26bd1910eba9
Cr-Commit-Position: refs/heads/master@{#345905}