Excessive flicker When Resizing Qt Quick Components Windows

When using new desktop components there is excessive flicker when resizing windows. This is not present (or not as noticeable) on non-component QML apps. The flicker takes the form of intermittent black flashes as the window is resized.

To reproduce: Run the text edit example ($QTDIR/qtquickcontrols/examples/quick/controls/text). Resize the window and observe. For comparison, run the equivalent widget based rich text edit example ($QTDIR/qtbase/examples/widgets/richtext).