Make extract_directories work even if no --root-dir was specified.
Make extract_directories work even if no --root-dir was specified.

trace_inputs tries to reduce the number of listed dependencies. When all files
in a directory are accessed, it replaces all the individual Results.File
instance by the Results.Directory instance representing the directory itself. It
is useful when hundreds of files are inside a directory and all of them are read
by an unit test.

The search is exhaustive and it is useful to have it stop at a directory. The
root directory used to be determined automatically but it is now explicit and
optional.

NOTRY=true
R=cmp@chromium.org
BUG=
TEST=


Review URL: https://chromiumcodereview.appspot.com/10541011

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@140604 0039d316-1c4b-4281-b951-d872f2087c98

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