Built Raspberry Pi 2 linux distro including Qt5.4 + QtWebKit + QML plugin using Yocto on fido branch See tutorial
Testing with the following QML script
root@raspberrypi2:~# more webkit.qml
import QtWebKit 3.0
WebView {
    url: "http://www.nokia.com"
    preferredWidth: 490
    preferredHeight: 400
    scale: 0.5
    smooth: false
}
When running this script I am getting the following error:
root@raspberrypi2:~# /usr/bin/qt5/qmlscene --platform eglfs webkit.qml 
Unable to query physical screen size, defaulting to 100 dpi.
To override, set QT_QPA_EGLFS_PHYSICAL_WIDTH and QT_QPA_EGLFS_PHYSICAL_HEIGHT (in millimeters).
QQmlPropertyCache: QQuickItem has FastProperty class info, but has not installed property accessors
Aborted
Any pointers?
 
                        
I had the same problem. The solution was to add the line
to the QML file.