[Qt] Clean up how the interaction engine is making use of ViewportAttributes

[Qt] Clean up how the interaction engine is making use of ViewportAttributes
https://bugs.webkit.org/show_bug.cgi?id=83895

Reviewed by Simon Hausmann.

Refactor how the interaction engine is using the ViewportAttributes
and get rid of the Contraints subclass.

Push the ViewportAttributes through to the QQuickWebViewPrivate class
and add some default values in the case the Legacy view is used.

* UIProcess/API/qt/qquickwebview.cpp:
(QQuickWebViewLegacyPrivate::QQuickWebViewLegacyPrivate):
(QQuickWebViewFlickablePrivate::didChangeViewportProperties):
* UIProcess/API/qt/qquickwebview_p_p.h:
(QQuickWebViewPrivate):
* UIProcess/API/qt/qwebviewportinfo.cpp:
(QWebViewportInfo::QWebViewportInfo):
(QWebViewportInfo::~QWebViewportInfo):
(QWebViewportInfo::currentScale):
(QWebViewportInfo::devicePixelRatio):
(QWebViewportInfo::initialScale):
(QWebViewportInfo::minimumScale):
(QWebViewportInfo::maximumScale):
(QWebViewportInfo::isScalable):
(QWebViewportInfo::layoutSize):
* UIProcess/qt/QtViewportInteractionEngine.cpp:
(WebKit::QtViewportInteractionEngine::cssScaleFromItem):
(WebKit::QtViewportInteractionEngine::itemScaleFromCSS):
(WebKit::QtViewportInteractionEngine::itemCoordFromCSS):
(WebKit::QtViewportInteractionEngine::innerBoundedCSSScale):
(WebKit::QtViewportInteractionEngine::outerBoundedCSSScale):
(WebKit::QtViewportInteractionEngine::zoomToAreaGestureEnded):
(WebKit::QtViewportInteractionEngine::setCSSScaleBounds):
(WebKit::QtViewportInteractionEngine::setCSSScale):
(WebKit::QtViewportInteractionEngine::pinchGestureStarted):
(WebKit::QtViewportInteractionEngine::pinchGestureRequestUpdate):
(WebKit::QtViewportInteractionEngine::pinchGestureEnded):
* UIProcess/qt/QtViewportInteractionEngine.h:
(QtViewportInteractionEngine):
(WebKit::QtViewportInteractionEngine::hadUserInteraction):
(WebKit::QtViewportInteractionEngine::setAllowsUserScaling):
(WebKit::QtViewportInteractionEngine::setContentToDevicePixelRatio):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114247 268f45cc-cd09-0410-ab3c-d52691b4dbfc