In checkToolTip(), the call to decorateToolTip() is not needed since it
does not affect the priority.

In showToolTip(), we can assume that checkToolTip() was called and thus
avoid a call to identifyMatch().

TextEditorWidgetPrivate::processTooltipRequest() is the only caller of
checkToolTip() and showToolTip().

Change-Id: I362c697754b6a29c9c0b34f85d3022f00e3e1031
Reviewed-by: David Schulz <david.schulz@qt.io>