code: public ClientConnectionTimingsBuilder pendingAcquisitionEnd() {
          checkState(pendingAcquisitionStartTimeMicros >= 0, "pendingAcquisitionStart() is not called yet.");
          checkState(!pendingAcquisitionEndSet, "pendingAcquisitionEnd() is already called.");
          pendingAcquisitionEndNanos = System.nanoTime();
          pendingAcquisitionEndSet = true;
          return this;
      }
docs: Sets the time when the client ended to wait for an existing connection attempt in order to use
  one connection for HTTP/2.
  
  @throws IllegalStateException if {@link #pendingAcquisitionStart()} is not invoked before calling this.