Reland "AppCache: Add padding to cross-origin responses."

This is a reland of 85b389caa7d725cdd31f59e9a2b79ff54804b7b7

Initialized CacheRecord::padding_size to 0.

Original change's description:
> AppCache: Add padding to cross-origin responses.
>
> Bug: 918293
> Change-Id: I4f16640f06feac009d6bbbb624951da6d2669f6c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1488059
> Commit-Queue: Staphany Park <staphany@chromium.org>
> Reviewed-by: Victor Costan <pwnall@chromium.org>
> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#644624}

Bug: 918293
Change-Id: Ie1d3f99c7e8a854d33255a4d66243da2ce16441c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539906
Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Staphany Park <staphany@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644719}
bool AppCacheDatabase::InsertGroup(const GroupRecord* record) {
  if (!LazyOpen(kCreateIfNeeded))
    return false;

  static const char kSql[] =
      "INSERT INTO Groups"
      "  (group_id, origin, manifest_url, creation_time, last_access_time,"
      "   last_full_update_check_time, first_evictable_error_time)"
      "  VALUES(?, ?, ?, ?, ?, ?, ?)";
  sql::Statement statement(db_->GetCachedStatement(SQL_FROM_HERE, kSql));
  statement.BindInt64(0, record->group_id);
  statement.BindString(1, SerializeOrigin(record->origin));
  statement.BindString(2, record->manifest_url.spec());
  statement.BindInt64(3, record->creation_time.ToInternalValue());
  statement.BindInt64(4, record->last_access_time.ToInternalValue());
  statement.BindInt64(5, record->last_full_update_check_time.ToInternalValue());
  statement.BindInt64(6, record->first_evictable_error_time.ToInternalValue());
  return statement.Run();
}

bool AppCacheDatabase::InsertGroup(const GroupRecord* record) {
  if (!LazyOpen(kCreateIfNeeded))
    return false;

  static const char kSql[] =
      "INSERT INTO Groups"
      "  (group_id, origin, manifest_url, creation_time, last_access_time,"
      "   last_full_update_check_time, first_evictable_error_time)"
      "  VALUES(?, ?, ?, ?, ?, ?, ?)";
  sql::Statement statement(db_->GetCachedStatement(SQL_FROM_HERE, kSql));
  statement.BindInt64(0, record->group_id);
  statement.BindString(1, SerializeOrigin(record->origin));
  statement.BindString(2, record->manifest_url.spec());
  statement.BindInt64(3, record->creation_time.ToInternalValue());
  statement.BindInt64(4, record->last_access_time.ToInternalValue());
  statement.BindInt64(5, record->last_full_update_check_time.ToInternalValue());
  statement.BindInt64(6, record->first_evictable_error_time.ToInternalValue());
  return statement.Run();
}
