Revert 155574 - [Chromoting] Refactoring DesktopEnvironment and moving screen/audio recorders to Cl…

Revert 155574 - [Chromoting] Refactoring DesktopEnvironment and moving screen/audio recorders to ClientSession.

This CL changes the way screen/audio recorders and event executors are managed. New DesktopEnvironmentFactory class is now used by ChromotingHost's owner to specify the kind of desktop environment (or virtual terminal) to be used by the host. Screen/audio recorders and event executors now owned by the ClientSession instance, so there is a separate set of recorders and stubs exists for each authenticated client session. Clients sessions can now be torn dowsn in parallel with the host shuttting down.

This is the 2nd attempt to land this change. This version includes:
- |ClientSession| objects are torn down asynchronously now.
- |ChromotingHost| now waits until all connections are torn down before deleting the session manager.

BUG=134694
TEST=remoting_unittests


Review URL: https://chromiumcodereview.appspot.com/10911152

TBR=alexeypa@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=155616

[alexeypa (please no reviews), 2012-09-09 04:05:21]

r155574 broke ClientSessionTest.ClamMouseEvents on Linux ASAN:
http://build.chromium.org/p/chromium.memory/buildstatus?builder=Linux%20ASAN%...