Break dependency of chrome.gyp:common on content.gyp:content_browser.

Break dependency of chrome.gyp:common on content.gyp:content_browser.

The dependency path is
  src/chrome/chrome.gyp:common ->
  src/components/components.gyp:policy_component ->
  src/components/components.gyp:user_prefs ->
  src/content/content.gyp:content_browser

This was introduced in https://codereview.chromium.org/102973005. The issue is
that URLBlacklistManager::RegisterProfilePrefs() uses a PrefServiceSyncable
which comes from user_prefs, and user_prefs depends on content::BrowserContext.

This fix splits the policy/common files into a policy_component_common target
that does not depend on user_prefs. chrome.gyp:common now depends on
policy_component_common, and chrome.gyp:browser depends on policy_component.

BUG=332030
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243567

[Joao da Silva, 2014-01-07 15:09:58]

This is ready for a first look. Took a while because it turns out that the
dependencies are not transitive in shared builds on win and mac.

PTAL, thanks!

[jochen (gone - plz use gerrit), 2014-01-07 15:19:59]

still doesn't build :)

[Joao da Silva, 2014-01-08 12:34:41]

This is ready for another look, and looks like it works on the bots too.

To avoid having to have 2 POLICY_EXPORT macros for policy_common and
policy_browser, I ended up taking Jochen's advice and doing the same that
content/content.gyp does.

PTAL, thanks!

[jochen (gone - plz use gerrit), 2014-01-08 12:38:23]

lgtm

[dconnelly, 2014-01-08 13:22:37]

blech. lgtm

[commit-bot: I haz the power, 2014-01-08 13:43:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/joaodasilva@chromium.org/124393003/370001

[commit-bot: I haz the power, 2014-01-08 15:36:38]

Change committed as 243567