[FIX] sap.ui.table.Table: incorrect header widths in a Dialog
[FIX] sap.ui.table.Table: incorrect header widths in a Dialog

- under the circumstances, getBoundingClientRect() returns unexpected values in Firefox v.49

Change-Id: I961e83b1b1aafb4ed299e25c7355e97d533c61f1
Fixes: https://github.com/SAP/openui5/issues/1138

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