Reduce parallel DNS resolutions to 6
Reduce parallel DNS resolutions to 6

Some routers black-hole resolutions beyond 6 in
parallel, and this should avoid the problem until
we craft a more adaptive implementation.

r=eroman
bug=122529

Review URL: http://codereview.chromium.org/10025005

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@131298 0039d316-1c4b-4281-b951-d872f2087c98

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