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

The constructor "GURL()" will create an invalid Url rather than "about:blank".
That causes xwalk failed to be launched with empty url, for example:
command "./xwalk" will be failed.

BUG=https://crosswalk-project.org/jira/browse/XWALK-958

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