Fix crash when a page action cannot load its icon.
Fix crash when a page action cannot load its icon.

This can happen legitmately if the icon has been moved or
corrupted on disk.

I think we are hitting it too frequently for that to be the
whole explanation, but since this code is moving around a
lot shortly, it seems prudent to put in the quick fix and
worry about what's really going on post-refactor.

BUG=25601
TEST=Remove an extension's page action icon from its folder after installation. Should not crash when attempting to show page action.

Review URL: http://codereview.chromium.org/339005

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@30069 0039d316-1c4b-4281-b951-d872f2087c98

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