Regression in implicit width calculations of Qt5 Row positioner

Compared to Qt 4.7 and qt-qml-team version of QtQuick 2.0, Row elements implicit width calculations have changed: now it incorrectly appends one extra spacing value to the total width. Execute attached row_spacing_bug.qml to see the problem, all three positioners shown on the example should look identical with the given parameters. Autotest case below fails on Qt5, but passes on older versions of QtQuick.

import QtQuick 2.0
import QtTest 1.0

Row {
    id: row
    spacing: 10
    Repeater {
        model: 5
        Item { width: 50; height: 50 }
    }
    TestCase {
        name: "Row"
        function test_width() {
            compare(row.width, 5*50 + 4*10); // fail: expected 290, actual 300
        }
    }
}