Revert "Xwalk can not be launched with empty url."
Revert "Xwalk can not be launched with empty url."

This has caused 6 tests to fail on Linux:

xwalk_browsertest:
        LoadGeolocationPage
        LoadURLAndClose
        TestMultiApp
xwalk_extensions_browsertest:
        CreateNewRuntimeAndNewRP
        OpenLinkInNewRuntimeAndNewRP
        OpenLinkInNewRuntimeAndSameRP

This reverts commit 723ccbedc0e0111e3da212b3b2831f59ac6ad5a9.

darktears/crosswalk,jondwillis/crosswalk,alex-zhang/crosswalk,crosswalk-project/crosswalk-efl,siovene/crosswalk,RafuCater/crosswalk,ZhengXinCN/crosswalk,alex-zhang/crosswalk,minggangw/crosswalk,leonhsl/crosswalk,Pluto-tv/crosswalk,shaochangbin/crosswalk,fujunwei/crosswalk,crosswalk-project/crosswalk,chinakids/crosswalk,hgl888/crosswalk,chinakids/crosswalk,PeterWangIntel/crosswalk,DonnaWuDongxia/crosswalk,RafuCater/crosswalk,jpike88/crosswalk,leonhsl/crosswalk,baleboy/crosswalk,huningxin/crosswalk,TheDirtyCalvinist/spacewalk,Bysmyyr/crosswalk,xzhan96/crosswalk,axinging/crosswalk,baleboy/crosswalk,darktears/crosswalk,hgl888/crosswalk-efl,lincsoon/crosswalk,tedshroyer/crosswalk,pk-sam/crosswalk,heke123/crosswalk,rakuco/crosswalk,marcuspridham/crosswalk,tomatell/crosswalk,heke123/crosswalk,PeterWangIntel/crosswalk,PeterWangIntel/crosswalk,jpike88/crosswalk,mrunalk/crosswalk,zeropool/crosswalk,zliang7/crosswalk,xzhan96/crosswalk,shaochangbin/crosswalk,bestwpw/crosswalk,hgl888/crosswalk,hgl888/crosswalk-efl,chuan9/crosswalk,xzhan96/crosswalk,leonhsl/crosswalk,jondwillis/crosswalk,XiaosongWei/crosswalk,hgl888/crosswalk-efl,baleboy/crosswalk,myroot/crosswalk,DonnaWuDongxia/crosswalk,hgl888/crosswalk,hgl888/crosswalk-efl,mrunalk/crosswalk,zliang7/crosswalk,huningxin/crosswalk,ZhengXinCN/crosswalk,lincsoon/crosswalk,fujunwei/crosswalk,fujunwei/crosswalk,myroot/crosswalk,qjia7/crosswalk,dreamsxin/crosswalk,hgl888/crosswalk,qjia7/crosswalk,hgl888/crosswalk-efl,amaniak/crosswalk,crosswalk-project/crosswalk,marcuspridham/crosswalk,minggangw/crosswalk,weiyirong/crosswalk-1,PeterWangIntel/crosswalk,siovene/crosswalk,stonegithubs/crosswalk,bestwpw/crosswalk,weiyirong/crosswalk-1,tomatell/crosswalk,XiaosongWei/crosswalk,zliang7/crosswalk,stonegithubs/crosswalk,minggangw/crosswalk,jpike88/crosswalk,jondwillis/crosswalk,dreamsxin/crosswalk,weiyirong/crosswalk-1,zeropool/crosswalk,alex-zhang/crosswalk,myroot/crosswalk,minggangw/crosswalk,tomatell/crosswalk,baleboy/crosswalk,rakuco/crosswalk,bestwpw/crosswalk,weiyirong/crosswalk-1,tedshroyer/crosswalk,tedshroyer/crosswalk,minggangw/crosswalk,crosswalk-project/crosswalk,mrunalk/crosswalk,zeropool/crosswalk,weiyirong/crosswalk-1,jpike88/crosswalk,amaniak/crosswalk,zliang7/crosswalk,Bysmyyr/crosswalk,myroot/crosswalk,tedshroyer/crosswalk,heke123/crosswalk,ZhengXinCN/crosswalk,jondwillis/crosswalk,marcuspridham/crosswalk,qjia7/crosswalk,lincsoon/crosswalk,stonegithubs/crosswalk,heke123/crosswalk,pk-sam/crosswalk,dreamsxin/crosswalk,hgl888/crosswalk,jondong/crosswalk,zliang7/crosswalk,crosswalk-project/crosswalk,huningxin/crosswalk,DonnaWuDongxia/crosswalk,chinakids/crosswalk,alex-zhang/crosswalk,amaniak/crosswalk,xzhan96/crosswalk,chinakids/crosswalk,qjia7/crosswalk,TheDirtyCalvinist/spacewalk,Pluto-tv/crosswalk,crosswalk-project/crosswalk,tomatell/crosswalk,dreamsxin/crosswalk,Bysmyyr/crosswalk,leonhsl/crosswalk,minggangw/crosswalk,darktears/crosswalk,DonnaWuDongxia/crosswalk,fujunwei/crosswalk,huningxin/crosswalk,zliang7/crosswalk,bestwpw/crosswalk,jondong/crosswalk,siovene/crosswalk,marcuspridham/crosswalk,chinakids/crosswalk,Bysmyyr/crosswalk,heke123/crosswalk,weiyirong/crosswalk-1,stonegithubs/crosswalk,alex-zhang/crosswalk,crosswalk-project/crosswalk-efl,PeterWangIntel/crosswalk,minggangw/crosswalk,chuan9/crosswalk,tedshroyer/crosswalk,DonnaWuDongxia/crosswalk,baleboy/crosswalk,zliang7/crosswalk,marcuspridham/crosswalk,huningxin/crosswalk,myroot/crosswalk,bestwpw/crosswalk,TheDirtyCalvinist/spacewalk,amaniak/crosswalk,lincsoon/crosswalk,axinging/crosswalk,jondwillis/crosswalk,jondwillis/crosswalk,chuan9/crosswalk,RafuCater/crosswalk,DonnaWuDongxia/crosswalk,Pluto-tv/crosswalk,heke123/crosswalk,alex-zhang/crosswalk,rakuco/crosswalk,fujunwei/crosswalk,rakuco/crosswalk,zliang7/crosswalk,Pluto-tv/crosswalk,tedshroyer/crosswalk,dreamsxin/crosswalk,shaochangbin/crosswalk,hgl888/crosswalk-efl,fujunwei/crosswalk,zeropool/crosswalk,axinging/crosswalk,crosswalk-project/crosswalk,bestwpw/crosswalk,qjia7/crosswalk,crosswalk-project/crosswalk-efl,jpike88/crosswalk,Pluto-tv/crosswalk,Pluto-tv/crosswalk,chinakids/crosswalk,mrunalk/crosswalk,jondong/crosswalk,bestwpw/crosswalk,heke123/crosswalk,jondong/crosswalk,Pluto-tv/crosswalk,jpike88/crosswalk,crosswalk-project/crosswalk-efl,darktears/crosswalk,Bysmyyr/crosswalk,pk-sam/crosswalk,shaochangbin/crosswalk,crosswalk-project/crosswalk,pk-sam/crosswalk,pk-sam/crosswalk,tomatell/crosswalk,zeropool/crosswalk,stonegithubs/crosswalk,darktears/crosswalk,axinging/crosswalk,siovene/crosswalk,lincsoon/crosswalk,chuan9/crosswalk,ZhengXinCN/crosswalk,siovene/crosswalk,zeropool/crosswalk,qjia7/crosswalk,zeropool/crosswalk,hgl888/crosswalk,rakuco/crosswalk,RafuCater/crosswalk,jondong/crosswalk,RafuCater/crosswalk,ZhengXinCN/crosswalk,crosswalk-project/crosswalk-efl,chuan9/crosswalk,shaochangbin/crosswalk,rakuco/crosswalk,stonegithubs/crosswalk,huningxin/crosswalk,Bysmyyr/crosswalk,mrunalk/crosswalk,marcuspridham/crosswalk,leonhsl/crosswalk,TheDirtyCalvinist/spacewalk,dreamsxin/crosswalk,minggangw/crosswalk,tomatell/crosswalk,TheDirtyCalvinist/spacewalk,crosswalk-project/crosswalk-efl,hgl888/crosswalk,XiaosongWei/crosswalk,alex-zhang/crosswalk,XiaosongWei/crosswalk,xzhan96/crosswalk,RafuCater/crosswalk,axinging/crosswalk,leonhsl/crosswalk,crosswalk-project/crosswalk-efl,baleboy/crosswalk,axinging/crosswalk,jondong/crosswalk,tedshroyer/crosswalk,jondong/crosswalk,shaochangbin/crosswalk,darktears/crosswalk,dreamsxin/crosswalk,ZhengXinCN/crosswalk,amaniak/crosswalk,baleboy/crosswalk,siovene/crosswalk,darktears/crosswalk,crosswalk-project/crosswalk,xzhan96/crosswalk,XiaosongWei/crosswalk,amaniak/crosswalk,amaniak/crosswalk,pk-sam/crosswalk,rakuco/crosswalk,jondwillis/crosswalk,lincsoon/crosswalk,Bysmyyr/crosswalk,fujunwei/crosswalk,hgl888/crosswalk-efl,baleboy/crosswalk,ZhengXinCN/crosswalk,rakuco/crosswalk,chuan9/crosswalk,axinging/crosswalk,RafuCater/crosswalk,jpike88/crosswalk,tomatell/crosswalk,pk-sam/crosswalk,heke123/crosswalk,hgl888/crosswalk,siovene/crosswalk,darktears/crosswalk,stonegithubs/crosswalk,myroot/crosswalk,marcuspridham/crosswalk,PeterWangIntel/crosswalk,chuan9/crosswalk,lincsoon/crosswalk,Bysmyyr/crosswalk,DonnaWuDongxia/crosswalk,TheDirtyCalvinist/spacewalk,jondong/crosswalk,PeterWangIntel/crosswalk,leonhsl/crosswalk,lincsoon/crosswalk,xzhan96/crosswalk,weiyirong/crosswalk-1,XiaosongWei/crosswalk,XiaosongWei/crosswalk,xzhan96/crosswalk,marcuspridham/crosswalk,mrunalk/crosswalk