When partitonalloc is built with "cookies", it stamps a value at the beginning and end of each allocation.  However, there is a problem with the reallocation path at https://cs.chromium.org/chromium/src/base/allocator/partition_allocator/partition_alloc.cc?l=1052

  if (actual_new_size == actual_old_size) {
    // Trying to allocate a block of size new_size would give us a block of
    // the same size as the one we've already got, so no point in doing
    // anything here.
    return ptr;
  }


When this is taken, the end cookie needs to be moved out of harm's way
since it will be overwritten by the caller when using the full size.

Additionally, the raw size bookkeeping needs to be updated to account for the new location of the cookie.