QWebEngine leaks memory with the software renderer

When a QWebEngineView is destroyed, the nodes in QQuickRenderControl::invalidate() are not cleaned since d->initialized is false (QQuickRenderControl::initialize(QOpenGLContext *gl) is not called with the software renderer). This means that DelegatedFrameNode::~DelegatedFrameNode, which holds a QVector<QSharedPointer<QSGTexture>>, is never called.

Steps to reproduce with QWebEngine_MemoryLeak.zip:

• Run QWebEngine_MemoryLeak
• Put a breakpoint on DelegatedFrameNode::DelegatedFrameNode and on DelegatedFrameNode::~DelegatedFrameNode
• Click on refresh
• With QQuickWindow::setSceneGraphBackend(QSGRendererInterface::Software) in main.cpp, the destructor is not called