[INTERNAL] sap.m.ComboBox:  improve rendering performance
[INTERNAL] sap.m.ComboBox:  improve rendering performance

Prevent layout thrashing after the list is rendered.

Change-Id: Ia33882f79494b642323e00bd2b99e00388601a68

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