Make sure that no decrypted text gets stuck in the plaintext buffer

Make sure that no decrypted text gets stuck in the plaintext buffer

When read events are enabled on a raw secure sockets, we need to fire
off a read event if there is data in the plaintext buffer. We cannot
rely on the underlying raw socket firing off another read event even
if it is open.

R=whesse@google.com
BUG=https://code.google.com/p/dart/issues/detail?id=8824

Committed: https://code.google.com/p/dart/source/detail?r=19247

[Bill Hesse, 2013-02-28 17:10:33]

LGTM.

[Søren Gjesse, 2013-02-28 17:16:10]

Committed patchset #1 manually as r19247 (presubmit successful).