DrawSurfaceWithShadow is supposed to ignore transforms but still support clipping.
It appears that DrawTargetD2D1 for some reason never actually implemented clipping.
The DrawImage calls on the DC just need to happen within the bounds of PrepareForDrawing
and FinalizeDrawing. Since PrepareForDrawing handles the overriding of the blend mode
via SetPrimitiveBlend, we need to use DrawImage with D2D1_COMPOSITE_MODE_SOURCE_OVER
so that it will blend appropriately.
Differential Revision: https://phabricator.services.mozilla.com/D140798