@Override
  public synchronized long now() {
    return now;
  }
Increments the clock's time gradually in several steps

<p>The clock will be incremented by tickMs amount repeatedly until it has progress by totalMs
from the given time when this call was made.

<p>This call is useful for working with animations in tests.

<p>In the end of this call, the call will progress by exactly totalMs, even if it means the
last tick of the clock is smaller than tickMs

@param tickMs the amount to tick the clock at each step
@param totalMs the total amount of time to elapse during the call
imagepipeline-base-test/src/main/java/com/facebook/imagepipeline/testing/FakeClock.java