Use new Widgets in mine_digger.
Use new Widgets in mine_digger.

I'm not sure I made it look better.  But it uses Widgets
instead of rolling its own Flex, etc.

R=ianh@google.com, cpu@chromium.org

Review URL: https://codereview.chromium.org/1201293003.

afandria/sky_engine,jamesr/sky_engine,TribeMedia/sky_engine,jamesr/flutter_engine,axinging/sky_engine,jason-simmons/sky_engine,jamesr/sky_engine,chinmaygarde/sky_engine,takaaptech/sky_engine,mdakin/engine,iansf/sky_engine,qiankunshe/sky_engine,mpcomplete/engine,jason-simmons/sky_engine,qiankunshe/sky_engine,zhangxq5012/sky_engine,mikejurka/engine,aam/engine,jason-simmons/flutter_engine,lyceel/engine,iansf/sky_engine,mpcomplete/flutter_engine,TribeMedia/sky_engine,jamesr/flutter_engine,devoncarew/sky_engine,krisgiesing/sky_engine,aam/engine,qiankunshe/sky_engine,qiankunshe/sky_engine,jason-simmons/flutter_engine,mpcomplete/flutter_engine,aam/engine,devoncarew/sky_engine,chinmaygarde/flutter_engine,tvolkert/engine,jason-simmons/flutter_engine,Hixie/sky_engine,jamesr/flutter_engine,mikejurka/engine,mpcomplete/flutter_engine,afandria/sky_engine,qiankunshe/sky_engine,axinging/sky_engine,jimsimon/sky_engine,lyceel/engine,TribeMedia/sky_engine,TribeMedia/sky_engine,mikejurka/engine,mdakin/engine,zhangxq5012/sky_engine,tvolkert/engine,mxia/engine,cdotstout/sky_engine,zhangxq5012/sky_engine,jamesr/sky_engine,zhangxq5012/sky_engine,axinging/sky_engine,takaaptech/sky_engine,abarth/sky_engine,cdotstout/sky_engine,mpcomplete/engine,iansf/sky_engine,chinmaygarde/sky_engine,lyceel/engine,krisgiesing/sky_engine,mxia/engine,axinging/sky_engine,chinmaygarde/sky_engine,mikejurka/engine,Hixie/sky_engine,tvolkert/engine,takaaptech/sky_engine,cdotstout/sky_engine,rmacnak-google/engine,jimsimon/sky_engine,xunmengfeng/engine,jimsimon/sky_engine,aam/engine,mpcomplete/engine,devoncarew/engine,tvolkert/engine,tvolkert/engine,rmacnak-google/engine,jimsimon/sky_engine,chinmaygarde/sky_engine,zhangxq5012/sky_engine,mikejurka/engine,mpcomplete/flutter_engine,mpcomplete/engine,krisgiesing/sky_engine,afandria/sky_engine,zhangxq5012/sky_engine,mdakin/engine,takaaptech/sky_engine,iansf/sky_engine,iansf/sky_engine,mpcomplete/engine,abarth/sky_engine,TribeMedia/sky_engine,takaaptech/sky_engine,xunmengfeng/engine,flutter/engine,afandria/sky_engine,abarth/sky_engine,lyceel/engine,devoncarew/engine,devoncarew/sky_engine,mxia/engine,chinmaygarde/flutter_engine,abarth/sky_engine,xunmengfeng/engine,abarth/sky_engine,jimsimon/sky_engine,krisgiesing/sky_engine,jason-simmons/flutter_engine,flutter/engine,jimsimon/sky_engine,qiankunshe/sky_engine,jamesr/sky_engine,takaaptech/sky_engine,cdotstout/sky_engine,abarth/sky_engine,iansf/sky_engine,jason-simmons/flutter_engine,jason-simmons/sky_engine,lyceel/engine,iansf/sky_engine,chinmaygarde/flutter_engine,jamesr/sky_engine,mpcomplete/engine,xunmengfeng/engine,mikejurka/engine,tvolkert/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,afandria/sky_engine,cdotstout/sky_engine,rmacnak-google/engine,mikejurka/engine,mxia/engine,chinmaygarde/flutter_engine,devoncarew/sky_engine,qiankunshe/sky_engine,Hixie/sky_engine,zhangxq5012/sky_engine,aam/engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,rmacnak-google/engine,mdakin/engine,mdakin/engine,krisgiesing/sky_engine,Hixie/sky_engine,TribeMedia/sky_engine,rmacnak-google/engine,jimsimon/sky_engine,krisgiesing/sky_engine,aam/engine,jason-simmons/sky_engine,Hixie/sky_engine,devoncarew/sky_engine,xunmengfeng/engine,mxia/engine,mxia/engine,jamesr/flutter_engine,qiankunshe/sky_engine,afandria/sky_engine,jason-simmons/flutter_engine,mxia/engine,mpcomplete/flutter_engine,afandria/sky_engine,takaaptech/sky_engine,devoncarew/sky_engine,Hixie/sky_engine,jamesr/flutter_engine,rmacnak-google/engine,lyceel/engine,jamesr/flutter_engine,iansf/sky_engine,abarth/sky_engine,jamesr/sky_engine,mdakin/engine,mikejurka/engine,flutter/engine,xunmengfeng/engine,xunmengfeng/engine,zhangxq5012/sky_engine,mdakin/engine,jamesr/sky_engine,axinging/sky_engine,jason-simmons/sky_engine,axinging/sky_engine,flutter/engine,aam/engine,chinmaygarde/sky_engine,jason-simmons/flutter_engine,zhangxq5012/sky_engine,jason-simmons/sky_engine,jimsimon/sky_engine,devoncarew/sky_engine,devoncarew/engine,chinmaygarde/flutter_engine,TribeMedia/sky_engine,devoncarew/engine,chinmaygarde/sky_engine,krisgiesing/sky_engine,mxia/engine,TribeMedia/sky_engine,aam/engine,Hixie/sky_engine,jamesr/flutter_engine,mpcomplete/engine,lyceel/engine,jamesr/flutter_engine,devoncarew/engine,tvolkert/engine,takaaptech/sky_engine,axinging/sky_engine,flutter/engine,TribeMedia/sky_engine,cdotstout/sky_engine,flutter/engine,chinmaygarde/sky_engine,flutter/engine,mdakin/engine,axinging/sky_engine,flutter/engine,takaaptech/sky_engine,mpcomplete/engine,devoncarew/engine,jason-simmons/flutter_engine,devoncarew/engine,mikejurka/engine,jimsimon/sky_engine,jamesr/flutter_engine,axinging/sky_engine,mpcomplete/flutter_engine,Hixie/sky_engine,jason-simmons/sky_engine,afandria/sky_engine