Remove unused is_background function

Change-Id: Ia540eac5f066ae95280c2f898370eddf0110c279

vp9/encoder/vp9_encodeframe.c

diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index fdc8e65..7660299 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -1282,36 +1282,6 @@
   }
 }
 
-static int is_background(const VP9_COMP *cpi, const TileInfo *const tile,
-                         int mi_row, int mi_col) {
-  // This assumes the input source frames are of the same dimension.
-  const int row8x8_remaining = tile->mi_row_end - mi_row;
-  const int col8x8_remaining = tile->mi_col_end - mi_col;
-  const int x = mi_col * MI_SIZE;
-  const int y = mi_row * MI_SIZE;
-  const int src_stride = cpi->Source->y_stride;
-  const uint8_t *const src = &cpi->Source->y_buffer[y * src_stride + x];
-  const int pre_stride = cpi->Last_Source->y_stride;
-  const uint8_t *const pre = &cpi->Last_Source->y_buffer[y * pre_stride + x];
-  int this_sad = 0;
-  int threshold = 0;
-
-  if (row8x8_remaining >= MI_BLOCK_SIZE &&
-      col8x8_remaining >= MI_BLOCK_SIZE) {
-    this_sad = cpi->fn_ptr[BLOCK_64X64].sdf(src, src_stride, pre, pre_stride);
-    threshold = (1 << 12);
-  } else {
-    int r, c;
-    for (r = 0; r < row8x8_remaining; r += 2)
-      for (c = 0; c < col8x8_remaining; c += 2)
-        this_sad += cpi->fn_ptr[BLOCK_16X16].sdf(src, src_stride,
-                                                 pre, pre_stride);
-    threshold = (row8x8_remaining * col8x8_remaining) << 6;
-  }
-
-  return this_sad < 2 * threshold;
-}
-
 static void update_state_rt(VP9_COMP *cpi, PICK_MODE_CONTEXT *ctx,
                             int mi_row, int mi_col, int bsize) {
   VP9_COMMON *const cm = &cpi->common;