gdi32: Pass the byte count to FONT_mbtowc in GetCharABCWidthsA.

dlls/gdi32/font.c

@@ -2317,7 +2317,7 @@ BOOL WINAPI GetCharABCWidthsA(HDC hdc, UINT firstChar, UINT lastChar,
     }
     str[i] = '\0';
 
-    wstr = FONT_mbtowc(hdc, str, -1, &wlen, NULL);
+    wstr = FONT_mbtowc(hdc, str, i, &wlen, NULL);
     if (wstr == NULL)
     {
         HeapFree(GetProcessHeap(), 0, str);

dlls/gdi32/tests/font.c

@@ -988,7 +988,6 @@ static void test_GetCharABCWidths(void)
         memset(full, 0xcc, sizeof full);
         ret = pGetCharABCWidthsA(hdc, 0x00, code, full);
         ok(ret, "GetCharABCWidthsA should have succeeded\n");
-        todo_wine
         ok(memcmp(&a[0], &full[code], sizeof(ABC)) == 0,
            "GetCharABCWidthsA info should match. codepage = %u\n", c[i].cs);