Bug 1577669 - Cast to uint32_t before left-shifting byte value by 24 bits. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D44132

--HG--
extra : moz-landing-system : lando

gfx/cairo/libpixman/src/pixman-sse2.c

@@ -6417,7 +6417,7 @@ sse2_fetch_a8 (pixman_iter_t *iter, const uint32_t *mask)
 
     while (w && (((uintptr_t)dst) & 15))
     {
-        *dst++ = *(src++) << 24;
+        *dst++ = (uint32_t)(*(src++)) << 24;
         w--;
     }
 
@@ -6444,7 +6444,7 @@ sse2_fetch_a8 (pixman_iter_t *iter, const uint32_t *mask)
 
     while (w)
     {
-	*dst++ = *(src++) << 24;
+	*dst++ = (uint32_t)(*(src++)) << 24;
 	w--;
     }