Use derived variable size for memcpy

Manually cherry-picked from aom/master:
bf2ad75a

Change-Id: I99f05e79ec8ad35a49bc124e6dd829ccc7d9cc36

av1/common/reconintra.c

@@ -1257,11 +1257,12 @@ static void build_intra_predictors_high(
     const int need_right = !!(extend_modes[mode] & NEED_ABOVERIGHT);
 #endif  // CONFIG_EXT_INTRA
     if (n_top_px > 0) {
-      memcpy(above_row, above_ref, n_top_px * 2);
+      memcpy(above_row, above_ref, n_top_px * sizeof(above_ref[0]));
       i = n_top_px;
       if (need_right && n_topright_px > 0) {
         assert(n_top_px == bs);
-        memcpy(above_row + bs, above_ref + bs, n_topright_px * 2);
+        memcpy(above_row + bs, above_ref + bs,
+               n_topright_px * sizeof(above_ref[0]));
         i += n_topright_px;
       }
       if (i < (bs << need_right))

test/convolve_test.cc

@@ -396,8 +396,8 @@ class ConvolveTest : public ::testing::TestWithParam<ConvolveParam> {
   void CopyOutputToRef() {
     memcpy(output_ref_, output_, kOutputBufferSize);
 #if CONFIG_AOM_HIGHBITDEPTH
-    memcpy(output16_ref_, output16_,
-           kOutputBufferSize * sizeof(output16_ref_[0]));
+    // Copy 16-bit pixels values. The effective number of bytes is double.
+    memcpy(output16_ref_, output16_, sizeof(output16_[0]) * kOutputBufferSize);
 #endif
   }