[[ Bug 12044 ]] Fix incomplete rendering of opaque group background when acceleratedRendering is enabled
Revert "[[ Bug 12044 ]] Fix incomplete rendering of opaque group background when acceleratedRendering is enabled"

This reverts commit 8e230bc8ff161b3e4efe390d09e728068e5e82e7.
[[ Bug 12044 ]] Reimplement fix by disabling scrolling layer mode for opaque groups with overscroll or patterned backgrounds
Merge branch 'bugfix-12044_rebase' into release-6.6.2