QmlProfiler: Add scaling support to paint events model

Change-Id: I04856628b7498df976d3b7db5539a1125060e9eb
Task-number: QTCREATORBUG-12337
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Draw selection boxes only as large as the items

Change-Id: I0f7f4f2a73c24faeff9c502b118e984938a27d25
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: replace calls to QVector::length() with QVector::size()

Like that we get a higher chance of staying compatible with Qt < 5.2.

Change-Id: Iecd6e1fbf75bd610917a38a22635a0d8e731738f
Reviewed-by: Kai Koehne <kai.koehne@digia.com>