Return the IAccessible interface of the deepest descent that contains the speficied point in view accessibility's accHitTest. 
Return the IAccessible interface of the deepest descent that contains the speficied point in view accessibility's accHitTest. 

Previously accHitTest would
1. Only return a direct child that contained the specified point (accHitTest was called repeatedly until it returned CHILDID_SELF).
2. Always return a VT_I4 variant for a view that has no children instead of returing an IAccessible interface (which didn't work with the AT programs for some reason).

BUG=none
TEST=Manual: NVDA reads views on mouse overwith no children on mouse over like toolbar buttons.
TEST=Manual: AccExplorer32 and Inspect32 can select views with no children.

Review URL: http://codereview.chromium.org/3890003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@63273 0039d316-1c4b-4281-b951-d872f2087c98

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