Use PCH by default in VS 2010.
Use PCH by default in VS 2010.

According to my testing, VS 2010 does not have problem (b) documented
at http://code.google.com/p/chromium/wiki/WindowsPrecompiledHeaders,
i.e. it rebuilds the PCH file when necessary because of
e.g. preprocessor flag changes.

Since we aren't using VS 2010 for official builds, if problem (a) (out
of memory) is encountered with VS 2010 when we make the switch to
using it for official builds, we can simply turn PCH off explicitly in
the include.gypi for the official bots.

This change has no effect on VS 2008 bots or users.

BUG=110001


Review URL: http://codereview.chromium.org/9139059

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@117845 0039d316-1c4b-4281-b951-d872f2087c98

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