This partly reverts commit ad28684b10.
Prior to that change, getBrush() would always end up calling
SetTransform on gradient/image brushes. This is important because, when
drawing text, we combine the current brush transform with the text
transform. If we don't reset the brush transform each time, these
transforms end up accumulating across frames.
The code contains a performance optimisation for cases where the world
transform is translation only. In this case instead of applying the
brush transformation first and then the world translation, the order is
reversed. The translation is applied first and then the brush
transformation.
Flipping the transformations however is only correct in the special case
when both transformations are translation only.
This change is practically a no-op, because if the affected branch is
taken, then the world transform was not applied, so transform is a
unity matrix. But if transform was non-unity, then the wrong ordering
would cause an observable error.
Logically the brush transformation is nested inside the world
transformation so the right order is applying the brush transform first
followed by the world transform.
