Remove BlobRegistry indirection since there is only one implementation.

BUG=

Review URL: https://chromiumcodereview.appspot.com/15851008

git-svn-id: svn://svn.chromium.org/blink/trunk@152746 bbb929c8-8fbe-4397-9dbb-9b2b20218538
void BlobData::detachFromCurrentThread()
{
    m_contentType = m_contentType.isolatedCopy();
    m_contentDisposition = m_contentDisposition.isolatedCopy();
    for (size_t i = 0; i < m_items.size(); ++i)
        m_items.at(i).detachFromCurrentThread();
}

void BlobData::detachFromCurrentThread()
{
    m_contentType = m_contentType.isolatedCopy();
    m_contentDisposition = m_contentDisposition.isolatedCopy();
    for (size_t i = 0; i < m_items.size(); ++i)
        m_items.at(i).detachFromCurrentThread();
}
