Access ChromotingHost::clients_ only on network thread.

Previously ChromotingHost was doing some work on the main thread and
some on the network thread. |clients_| and some other members were
accessed without lock on both of these threads. Moved most of the
ChromotingHost activity to the network thread to avoid possible
race conditions.

BUG=96325
TEST=Chromoting works

Review URL: http://codereview.chromium.org/8495024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@109556 0039d316-1c4b-4281-b951-d872f2087c98
void HostNPScriptObject::PostLogDebugInfo(const std::string& message) {
  if (plugin_message_loop_proxy_->BelongsToCurrentThread()) {
    if (am_currently_logging_)
      return;
  }

  plugin_message_loop_proxy_->PostTask(
      FROM_HERE, base::Bind(&HostNPScriptObject::LogDebugInfo,
                            base::Unretained(this), message));
}

void HostNPScriptObject::PostLogDebugInfo(const std::string& message) {
  if (plugin_message_loop_proxy_->BelongsToCurrentThread()) {
    if (am_currently_logging_)
      return;
  }

  plugin_message_loop_proxy_->PostTask(
      FROM_HERE, base::Bind(&HostNPScriptObject::LogDebugInfo,
                            base::Unretained(this), message));
}
