Fix <sky-input> data binding when editing deletes the last char.
Fix <sky-input> data binding when editing deletes the last char.

contenteditable would remove the Text node inside the
editable area which would mean setting the value attr
of the <sky-input> would stop updating the editable
area.

Instead we add the text back if editing removed it.

R=abarth@chromium.org, ojan@chromium.org

Review URL: https://codereview.chromium.org/788953006

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