Fix LogMan tracer to work correctly when process ids are reused.
Fix LogMan tracer to work correctly when process ids are reused.

Reproduced with:
  isolate.py trace -r .../net_unittests.results
  isolate.py read -r .../net_unittests.results

It happens randomly whenever Windows decides to reuse a process id so it tends
to happens often with browser_tests.

This happened because stale processes are not removed from the map but set to
None instead.

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


Review URL: https://chromiumcodereview.appspot.com/10824409

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@152755 0039d316-1c4b-4281-b951-d872f2087c98

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