Build the list of key system/container/codec combinations at runtime.
Build the list of key system/container/codec combinations at runtime.

This is more similar to how net/base/mime_util.cc works and avoids combinatorial explosion.

TEST=encrypted-media-can-play-type*.html

Review URL: https://chromiumcodereview.appspot.com/11081005

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@161026 0039d316-1c4b-4281-b951-d872f2087c98

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