Fix a bug when exiting Mac Chrome with in progress downloads.
Fix a bug when exiting Mac Chrome with in progress downloads.

If the user has closed all browser windows and then tries to exit
with downloads in progress, Mac Chrome would just quit. This CL
handles the case of exiting without any windows open.

BUG=15899 (http://crbug.com/15899)
TEST=Start a download, close all windows then try to exit. Chrome
     will now prompt the user with an exit confirm dialog.
Review URL: http://codereview.chromium.org/164273

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@22973 0039d316-1c4b-4281-b951-d872f2087c98

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