Serious cleanup of SpdyFramer compression code:

      * Move the compression logic into SerializeNameValueBlock.
 * Get rid of accessory methods like 'IsCompressible' and 'CompressControlFrame'.
 * Get us a few steps closer to removing SpdyControlFrame.
 * Add some logic to SpdyFrameBuilder to be able to build test frames more easily.
 * Remove need for 'compressed' argument in CreateSynStream, CreateSynReply and CreateHeaders. The argument has been left in with a DCHECK ensuring correct behavior in order to illustrate that zero behavioral change has been made. It will be removed in a follow-up CL.
 * Lots of other cleanup.

Zero change to on-the-wire results and behavior.

This lands server change 42232412.

Also replaces OnControlFrameCompressed with OnSynStreamCompressed.

Also maintains Chrome-specific behavior, like USE_SYSTEM_ZLIB switching and the CRIME fixes in r151720.

Also pass through enable_compression_ flag in SpdySession.

BUG=139744

Review URL: https://codereview.chromium.org/12263029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182753 0039d316-1c4b-4281-b951-d872f2087c98