Make QSGCanvas::grabFrameBuffer() more reliable
Make QSGCanvas::grabFrameBuffer() more reliable

jfaust/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,crobertd/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,jfaust/qtdeclarative,mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,jfaust/qtdeclarative,jfaust/qtdeclarative,mgrunditz/qtdeclarative-2d