Abstract BrowserProcess dependency from VariationsService

Abstract BrowserProcess dependency from VariationsService

As part of componentizing VariationsService, eliminate its knowledge
of BrowserProcess, instead obtaining the necessary information via
VariationsServiceClient.

BUG=516678
Committed: https://crrev.com/0368caee9a5c42194309a29d871cba48a5aeb2e9
Cr-Commit-Position: refs/heads/master@{#345087}

[blundell, 2015-08-17 18:54:38]

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

[blundell, 2015-08-17 18:54:39]

Thanks for the review on the first CL. The process now is just straightforward
abstraction of //chrome- and //content-level dependencies through
VariationsServiceClient.

[blundell, 2015-08-19 08:57:03]

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

[blundell, 2015-08-19 08:57:03]

over to Alexei.

[Alexei Svitkine (slow), 2015-08-24 14:28:13]

lgtm

[blundell, 2015-08-24 15:42:46]

The CQ bit was checked by blundell@chromium.org

[blundell, 2015-08-24 15:42:46]

The patchset sent to the CQ was uploaded after l-g-t-m from
asvitkine@chromium.org
Link to the patchset: https://codereview.chromium.org/1298743004/#ps10001
(title: "Rebase")

[commit-bot: I haz the power, 2015-08-24 15:43:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1298743004/10001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1298743004/10001

[commit-bot: I haz the power, 2015-08-24 16:22:30]

Committed patchset #2 (id:10001)

[commit-bot: I haz the power, 2015-08-24 16:23:19]

Patchset 2 (id:??) landed as
https://crrev.com/0368caee9a5c42194309a29d871cba48a5aeb2e9
Cr-Commit-Position: refs/heads/master@{#345087}