Changes tab dragging code to ignore WS_EX_TRANSPARENT and WS_EX_LAYERED windows. Here's the comment I'm adding as to why:
Changes tab dragging code to ignore WS_EX_TRANSPARENT and
WS_EX_LAYERED windows. Here's the comment I'm adding as to why:

      // Mouse events fall through WS_EX_TRANSPARENT windows, so we ignore them.
      //
      // WS_EX_LAYERED is trickier. Apps like Switcher create a totally
      // transparent WS_EX_LAYERED window that is always on top. If we don't
      // ignore WS_EX_LAYERED windows and there are totally transparent
      // WS_EX_LAYERED windows then there are effectively holes on the screen
      // that the user can't reattach tabs to. So we ignore them. This is a bit
      // problematic in so far as WS_EX_LAYERED windows need not be totally
      // transparent in which case we treat chrome windows as not being obscured
      // when they really are, but this is better than not being able to
      // reattach tabs.

BUG=12580 10742
TEST=none

Review URL: http://codereview.chromium.org/3383004

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@59562 0039d316-1c4b-4281-b951-d872f2087c98

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