class ActiveRecord::ConnectionAdapters::ConnectionPool::BiasableQueue::BiasedConditionVariable

def initialize(lock, other_cond, preferred_thread)

+signal+ and +wait+ methods are only called while holding a lock
semantics of condition variables guarantee that +broadcast+, +broadcast_on_biased+,
:nodoc:
:nodoc:
biased to some thread.
Adds the ability to turn a basic fair FIFO queue into one 
def initialize(lock, other_cond, preferred_thread)
  @real_cond = lock.new_cond
  @other_cond = other_cond
  @preferred_thread = preferred_thread
  @num_waiting_on_real_cond = 0
end