base: Suggest forward declare DefaultSingletonTraits in header files.
base: Suggest forward declare DefaultSingletonTraits in header files.

Instead of including singleton.h in header files we can forward declare it,
and include only in the source file.

There is also a presubmit check for this, I didn't know ;)

R=willchan@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10835029

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@149095 0039d316-1c4b-4281-b951-d872f2087c98

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