Fixes bug in dragging tabs. Specifically if you only have one window with one tab, drag the tab, and while dragging click and release the right mouse button we get all confused. This is because we get two OnMousePressed events in a row, which results in cancelling out the current drag which doesn't work well when only one tab with one window is left.
Fixes bug in dragging tabs. Specifically if you only have one window
with one tab, drag the tab, and while dragging click and release the
right mouse button we get all confused. This is because we get two
OnMousePressed events in a row, which results in cancelling out the
current drag which doesn't work well when only one tab with one window
is left.

BUG=10800
TEST=see bug

Review URL: http://codereview.chromium.org/100169

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@14870 0039d316-1c4b-4281-b951-d872f2087c98

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