[FIX] core.HTML: Render content correctly on switching visibility
[FIX] core.HTML: Render content correctly on switching visibility

Fixes https://github.com/SAP/openui5/issues/231
Change-Id: I7fe4355d4a8a4c6dc8d8a70cb364f9dfbb4c5d5e

SAP/openui5,nzamani/openui5,cschuff/openui5,SQCLabs/openui5,nzamani/openui5,cschuff/openui5,SAP/openui5,olirogers/openui5,SAP/openui5,cschuff/openui5,nzamani/openui5,olirogers/openui5,SQCLabs/openui5,SQCLabs/openui5,olirogers/openui5,SAP/openui5