Fixed default backgroud color issue with iframe mode
Fixed default backgroud color issue with iframe mode

jtark/tinymce,rxl194/tinymce,fillabs/TinySpecMCE,adaptiffdesigns/tinymce,gencer/tinymce,aduth/tinymce,TeamupCom/tinymce,leofeyer/tinymce,jashua212/tinymce,leofeyer/tinymce,shilpi230/tinymce,ETSI-CTI/TinySpecMCE,ikuchmin/tinymce,danielpunkass/tinymce,danielpunkass/tinymce,gencer/tinymce,rbecheras/tinymce,aduth/tinymce,sachgits/tinymce,nikolas/tinymce,gabixdev/tinymce,pmpl-5/tinymce,nikolas/tinymce,tinymce/tinymce,rxl194/tinymce,VioletLife/tinymce,mplank/tinymce,kencheung/tinymce,Razzwan/tinymce,nbcp/tinymce,simachewh/tinymce,pmpl-5/tinymce,sjbufton/tinymce,blakewallan/tinymce,fashionsun/tinymce,enfold/tinymce,FernCreek/tinymce,ChristophKaser/tinymce,endjin/tinymce,Zimbra/tinymce,fashionsun/tinymce,tinymce/tinymce,nbcp/tinymce,fillabs/TinySpecMCE,MediehusetTek/tinymce,gabixdev/tinymce,fhchina/tinymce,Kindling/tinymce,VioletLife/tinymce,FernCreek/tinymce,1099511627776/tinymce,Kindling/tinymce,jtark/tinymce,rednose-public/tinymce,bsuh/tinymce,Zimbra/tinymce,TeamupCom/tinymce,blakewallan/tinymce,sjbufton/tinymce,dziemian007/tinymce,M4R7iNP/tinymce,ETSI-CTI/TinySpecMCE,simachewh/tinymce,howanghk/tinymce,ChristophKaser/tinymce,shilpi230/tinymce,M4R7iNP/tinymce,rednose-public/tinymce,endjin/tinymce,enfold/tinymce,mplank/tinymce,bsuh/tinymce,kencheung/tinymce,henrythewasp/tinymce,Shopify/tinymce,Razzwan/tinymce,ice8lue/tinymce,adaptiffdesigns/tinymce,support-dot-com/tinymce,howanghk/tinymce,ikuchmin/tinymce,henrythewasp/tinymce,FernCreek/tinymce,1099511627776/tinymce,danchr/tinymce,tinymce/tinymce,support-dot-com/tinymce,sachgits/tinymce,danielpunkass/tinymce,fhchina/tinymce,danchr/tinymce,jashua212/tinymce,dziemian007/tinymce,ice8lue/tinymce,MediehusetTek/tinymce,rbecheras/tinymce