Add the SandboxedDMGParser and wire it up to the DownloadProtectionService.

BUG=496898,464083
R=isherman@chromium.org, kenrb@chromium.org, mattm@chromium.org, thestig@chromium.org

Review URL: https://codereview.chromium.org/1299223006 .

Cr-Commit-Position: refs/heads/master@{#344876}
void DownloadProtectionService::CheckDownloadUrl(
    const content::DownloadItem& item,
    const CheckDownloadCallback& callback) {
  DCHECK(!item.GetUrlChain().empty());
  scoped_refptr<DownloadUrlSBClient> client(
      new DownloadUrlSBClient(item, callback, ui_manager_, database_manager_));
  BrowserThread::PostTask(
        BrowserThread::IO,
        FROM_HERE,
        base::Bind(&DownloadUrlSBClient::StartCheck, client));
}

void DownloadProtectionService::CheckDownloadUrl(
    const content::DownloadItem& item,
    const CheckDownloadCallback& callback) {
  DCHECK(!item.GetUrlChain().empty());
  scoped_refptr<DownloadUrlSBClient> client(
      new DownloadUrlSBClient(item, callback, ui_manager_, database_manager_));
  BrowserThread::PostTask(
        BrowserThread::IO,
        FROM_HERE,
        base::Bind(&DownloadUrlSBClient::StartCheck, client));
}
