Adding metric to tracking the unlock screen request code path
Adding metric to tracking the unlock screen request code path

For unlocking the screen we enter a code path were we do a method call, get a
empty reply, and then receive a signal to indicate that chrome can perform the
UI actions for screen unlocking. We have encountered issues where communication
on this path has failed. A fix for the specific bug has been landed, but we
would still like to track information about how we progress through this path to
detect future issues.

The metric that is being introduced is
"LockScreen.UnlockScreenPath".

BUG=chromium-os:31541
TEST=Built Chrome with CL.
     Built ChromeOS image using CL.
     Ran image to confirm that no regressions had been introduced.
     Ran image and locked screen. Checked histogram populated.


Review URL: https://chromiumcodereview.appspot.com/10540013

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@140763 0039d316-1c4b-4281-b951-d872f2087c98

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