Cache blur shaders only when blur is enabled

Change-Id: I5dd5f90e70d99e2ff8213177c81345171694a1f2

Test: build for R4 confirm with perfetto blur shaders attempted only when property is set

Bug: b/190499047
Change-Id: I3053e6b0711fc77b97f216019de99211d0b842cc
1 file changed