Fixes race condition in displaying error pages. In particular it was possible for an error page to be shown after another load, resulting in cancelling the other load. Here's the sequence that can trigger it: . load page that results in error page (eg http://cnn.co), in RVH1. . trigger loading of error page . load correct page (eg http://cnn.com) in RVH2. This triggers a stop   in RVH1. . error page finishes loading. Navigation completes, notifies browser   and browser swaps back to RVH1.
Fixes race condition in displaying error pages. In particular it was
possible for an error page to be shown after another load, resulting
in cancelling the other load. Here's the sequence that can trigger it:
. load page that results in error page (eg http://cnn.co), in RVH1.
. trigger loading of error page
. load correct page (eg http://cnn.com) in RVH2. This triggers a stop
  in RVH1.
. error page finishes loading. Navigation completes, notifies browser
  and browser swaps back to RVH1.

BUG=79515
TEST=none
R=jamesr@chromium.org

Review URL: http://codereview.chromium.org/7004024

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@85280 0039d316-1c4b-4281-b951-d872f2087c98

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