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


Review URL: http://codereview.chromium.org/9696034

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@126626 0039d316-1c4b-4281-b951-d872f2087c98

Jonekee/chromium.src,mohamed--abdel-maksoud/chromium.src,M4sse/chromium.src,patrickm/chromium.src,zcbenz/cefode-chromium,keishi/chromium,chuan9/chromium-crosswalk,Jonekee/chromium.src,zcbenz/cefode-chromium,anirudhSK/chromium,Fireblend/chromium-crosswalk,krieger-od/nwjs_chromium.src,Chilledheart/chromium,junmin-zhu/chromium-rivertrail,mohamed--abdel-maksoud/chromium.src,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk-efl,mogoweb/chromium-crosswalk,patrickm/chromium.src,hujiajie/pa-chromium,axinging/chromium-crosswalk,junmin-zhu/chromium-rivertrail,pozdnyakov/chromium-crosswalk,rogerwang/chromium,robclark/chromium,markYoungH/chromium.src,Chilledheart/chromium,M4sse/chromium.src,krieger-od/nwjs_chromium.src,pozdnyakov/chromium-crosswalk,dushu1203/chromium.src,robclark/chromium,nacl-webkit/chrome_deps,Pluto-tv/chromium-crosswalk,patrickm/chromium.src,anirudhSK/chromium,zcbenz/cefode-chromium,timopulkkinen/BubbleFish,pozdnyakov/chromium-crosswalk,hgl888/chromium-crosswalk,ondra-novak/chromium.src,nacl-webkit/chrome_deps,rogerwang/chromium,timopulkkinen/BubbleFish,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,robclark/chromium,bright-sparks/chromium-spacewalk,Chilledheart/chromium,krieger-od/nwjs_chromium.src,M4sse/chromium.src,M4sse/chromium.src,krieger-od/nwjs_chromium.src,hujiajie/pa-chromium,rogerwang/chromium,crosswalk-project/chromium-crosswalk-efl,markYoungH/chromium.src,M4sse/chromium.src,markYoungH/chromium.src,crosswalk-project/chromium-crosswalk-efl,littlstar/chromium.src,keishi/chromium,mogoweb/chromium-crosswalk,bright-sparks/chromium-spacewalk,rogerwang/chromium,mogoweb/chromium-crosswalk,bright-sparks/chromium-spacewalk,hgl888/chromium-crosswalk,hujiajie/pa-chromium,junmin-zhu/chromium-rivertrail,crosswalk-project/chromium-crosswalk-efl,timopulkkinen/BubbleFish,junmin-zhu/chromium-rivertrail,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,ltilve/chromium,rogerwang/chromium,ChromiumWebApps/chromium,patrickm/chromium.src,mohamed--abdel-maksoud/chromium.src,Chilledheart/chromium,nacl-webkit/chrome_deps,hgl888/chromium-crosswalk,littlstar/chromium.src,fujunwei/chromium-crosswalk,ondra-novak/chromium.src,hgl888/chromium-crosswalk,pozdnyakov/chromium-crosswalk,hgl888/chromium-crosswalk-efl,M4sse/chromium.src,robclark/chromium,ltilve/chromium,keishi/chromium,fujunwei/chromium-crosswalk,krieger-od/nwjs_chromium.src,Chilledheart/chromium,dednal/chromium.src,fujunwei/chromium-crosswalk,patrickm/chromium.src,rogerwang/chromium,keishi/chromium,bright-sparks/chromium-spacewalk,mohamed--abdel-maksoud/chromium.src,keishi/chromium,Fireblend/chromium-crosswalk,nacl-webkit/chrome_deps,timopulkkinen/BubbleFish,jaruba/chromium.src,keishi/chromium,crosswalk-project/chromium-crosswalk-efl,jaruba/chromium.src,axinging/chromium-crosswalk,ChromiumWebApps/chromium,rogerwang/chromium,bright-sparks/chromium-spacewalk,jaruba/chromium.src,hgl888/chromium-crosswalk-efl,Jonekee/chromium.src,PeterWangIntel/chromium-crosswalk,M4sse/chromium.src,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,robclark/chromium,jaruba/chromium.src,PeterWangIntel/chromium-crosswalk,anirudhSK/chromium,jaruba/chromium.src,Fireblend/chromium-crosswalk,timopulkkinen/BubbleFish,zcbenz/cefode-chromium,jaruba/chromium.src,dushu1203/chromium.src,dednal/chromium.src,markYoungH/chromium.src,M4sse/chromium.src,keishi/chromium,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,littlstar/chromium.src,bright-sparks/chromium-spacewalk,pozdnyakov/chromium-crosswalk,dednal/chromium.src,mogoweb/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,ondra-novak/chromium.src,Fireblend/chromium-crosswalk,Just-D/chromium-1,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,nacl-webkit/chrome_deps,mohamed--abdel-maksoud/chromium.src,chuan9/chromium-crosswalk,Chilledheart/chromium,junmin-zhu/chromium-rivertrail,mogoweb/chromium-crosswalk,jaruba/chromium.src,ChromiumWebApps/chromium,Fireblend/chromium-crosswalk,nacl-webkit/chrome_deps,dushu1203/chromium.src,robclark/chromium,mogoweb/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,junmin-zhu/chromium-rivertrail,ChromiumWebApps/chromium,zcbenz/cefode-chromium,M4sse/chromium.src,rogerwang/chromium,M4sse/chromium.src,patrickm/chromium.src,rogerwang/chromium,ChromiumWebApps/chromium,robclark/chromium,Jonekee/chromium.src,ChromiumWebApps/chromium,chuan9/chromium-crosswalk,pozdnyakov/chromium-crosswalk,junmin-zhu/chromium-rivertrail,mohamed--abdel-maksoud/chromium.src,Jonekee/chromium.src,nacl-webkit/chrome_deps,Jonekee/chromium.src,ChromiumWebApps/chromium,mogoweb/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,nacl-webkit/chrome_deps,Fireblend/chromium-crosswalk,jaruba/chromium.src,dushu1203/chromium.src,zcbenz/cefode-chromium,markYoungH/chromium.src,timopulkkinen/BubbleFish,Pluto-tv/chromium-crosswalk,anirudhSK/chromium,junmin-zhu/chromium-rivertrail,ltilve/chromium,timopulkkinen/BubbleFish,axinging/chromium-crosswalk,ondra-novak/chromium.src,ondra-novak/chromium.src,ltilve/chromium,bright-sparks/chromium-spacewalk,dednal/chromium.src,timopulkkinen/BubbleFish,anirudhSK/chromium,dednal/chromium.src,ltilve/chromium,hgl888/chromium-crosswalk,Chilledheart/chromium,mohamed--abdel-maksoud/chromium.src,hujiajie/pa-chromium,TheTypoMaster/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,littlstar/chromium.src,axinging/chromium-crosswalk,Jonekee/chromium.src,Pluto-tv/chromium-crosswalk,mogoweb/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,dednal/chromium.src,hujiajie/pa-chromium,junmin-zhu/chromium-rivertrail,ltilve/chromium,zcbenz/cefode-chromium,robclark/chromium,ondra-novak/chromium.src,Just-D/chromium-1,hujiajie/pa-chromium,hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,dednal/chromium.src,markYoungH/chromium.src,mohamed--abdel-maksoud/chromium.src,Just-D/chromium-1,anirudhSK/chromium,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,rogerwang/chromium,hgl888/chromium-crosswalk,anirudhSK/chromium,nacl-webkit/chrome_deps,TheTypoMaster/chromium-crosswalk,dednal/chromium.src,fujunwei/chromium-crosswalk,hujiajie/pa-chromium,PeterWangIntel/chromium-crosswalk,markYoungH/chromium.src,anirudhSK/chromium,keishi/chromium,nacl-webkit/chrome_deps,dednal/chromium.src,jaruba/chromium.src,bright-sparks/chromium-spacewalk,Just-D/chromium-1,hujiajie/pa-chromium,Pluto-tv/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,anirudhSK/chromium,dushu1203/chromium.src,bright-sparks/chromium-spacewalk,ondra-novak/chromium.src,Chilledheart/chromium,jaruba/chromium.src,markYoungH/chromium.src,Jonekee/chromium.src,Pluto-tv/chromium-crosswalk,ltilve/chromium,hujiajie/pa-chromium,nacl-webkit/chrome_deps,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,chuan9/chromium-crosswalk,hujiajie/pa-chromium,littlstar/chromium.src,hgl888/chromium-crosswalk-efl,littlstar/chromium.src,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,dushu1203/chromium.src,zcbenz/cefode-chromium,dushu1203/chromium.src,krieger-od/nwjs_chromium.src,hgl888/chromium-crosswalk-efl,ChromiumWebApps/chromium,pozdnyakov/chromium-crosswalk,pozdnyakov/chromium-crosswalk,dushu1203/chromium.src,timopulkkinen/BubbleFish,Fireblend/chromium-crosswalk,mogoweb/chromium-crosswalk,robclark/chromium,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,krieger-od/nwjs_chromium.src,PeterWangIntel/chromium-crosswalk,dushu1203/chromium.src,markYoungH/chromium.src,fujunwei/chromium-crosswalk,dushu1203/chromium.src,ChromiumWebApps/chromium,TheTypoMaster/chromium-crosswalk,anirudhSK/chromium,crosswalk-project/chromium-crosswalk-efl,axinging/chromium-crosswalk,Jonekee/chromium.src,dednal/chromium.src,hujiajie/pa-chromium,dushu1203/chromium.src,patrickm/chromium.src,keishi/chromium,ChromiumWebApps/chromium,ondra-novak/chromium.src,hgl888/chromium-crosswalk-efl,zcbenz/cefode-chromium,fujunwei/chromium-crosswalk,mogoweb/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,ltilve/chromium,krieger-od/nwjs_chromium.src,axinging/chromium-crosswalk,krieger-od/nwjs_chromium.src,anirudhSK/chromium,krieger-od/nwjs_chromium.src,markYoungH/chromium.src,ltilve/chromium,Fireblend/chromium-crosswalk,littlstar/chromium.src,keishi/chromium,TheTypoMaster/chromium-crosswalk,junmin-zhu/chromium-rivertrail,axinging/chromium-crosswalk,axinging/chromium-crosswalk,markYoungH/chromium.src,Jonekee/chromium.src,ondra-novak/chromium.src,timopulkkinen/BubbleFish,patrickm/chromium.src,ChromiumWebApps/chromium,patrickm/chromium.src,crosswalk-project/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,anirudhSK/chromium,Fireblend/chromium-crosswalk,zcbenz/cefode-chromium,pozdnyakov/chromium-crosswalk,Just-D/chromium-1,Jonekee/chromium.src,pozdnyakov/chromium-crosswalk,junmin-zhu/chromium-rivertrail,Chilledheart/chromium,littlstar/chromium.src,M4sse/chromium.src,zcbenz/cefode-chromium,pozdnyakov/chromium-crosswalk,hgl888/chromium-crosswalk,jaruba/chromium.src,fujunwei/chromium-crosswalk,timopulkkinen/BubbleFish,hgl888/chromium-crosswalk-efl,dednal/chromium.src,chuan9/chromium-crosswalk,keishi/chromium,ChromiumWebApps/chromium,hgl888/chromium-crosswalk-efl,robclark/chromium,PeterWangIntel/chromium-crosswalk