Revert "Bypass filtering of strengh=0 cdef blocks for speed."

This reverts commit df6793d.

src/cdef.rs

@@ -260,12 +260,6 @@ pub fn cdef_filter_superblock(fi: &FrameInvariants,
         cdef_sec_uv_strength += 1;
     }
 
-    if cdef_y_strength == 0 && cdef_uv_strength == 0 {
-        // bypass filtering for speed
-        // this assumes that out_frame is already filled with in_frame's contents
-        return
-    }
-
     // Each direction block is 8x8 in y, potentially smaller if subsampled in chroma
     for by in 0..8 {
         for bx in 0..8 {
@@ -369,7 +363,6 @@ pub fn cdef_filter_frame(fi: &FrameInvariants, rec: &mut Frame, bc: &mut BlockCo
                 }
             }
             // copy current row from rec if we're in data, or pad if we're in first two rows/last N rows
-            // all pixel data must be copied, as cdef_filter_superblock may skip writing pixels for strength=0
             {
                 let mut cdef_slice = cdef_frame.planes[p].mut_slice(&PlaneOffset { x: 2, y: row as isize });
                 let mut cdef_row = &mut cdef_slice.as_mut_slice()[..rec_w];