Avoid creating BrowserThreadGlobals when we don't need to.

Avoid creating BrowserThreadGlobals when we don't need to.

In tessts, it is possible for BrowserThread static methods like
IsWellKnownThread to get called when no message loops exists. We can
infer the answer for many methods from the fact the globals are
NULL without having to construct them. (constructing them can have the
undesireable side effect in these cases of hitting DCHECK for
MessageLoop::current() in the SequencedWorkerPool constructor)

BUG=117940
TEST=out/Debug/unit_tests --gtest_filter=TemplateURLPrepopulateDataTest.ProvidersFromPrefs


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=126626

[brettw, 2012-03-13 16:31:22]

lgtm

[commit-bot: I haz the power, 2012-03-13 16:37:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/joth@chromium.org/9696034/2002

[akalin, 2012-03-13 16:42:31]

On 2012/03/13 16:37:35, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
> https://chromium-status.appspot.com/cq/joth%40chromium.org/9696034/2002

lgtm

[commit-bot: I haz the power, 2012-03-13 21:35:24]

Try job failure for 9696034-2002 (retry) (retry) on win_rel for step
"browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2012-03-14 09:41:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/joth@chromium.org/9696034/2002

[commit-bot: I haz the power, 2012-03-14 11:57:51]

Change committed as 126626