This method (currently @hide) discards all cached buffers for the ImageReader, which can be useful to free up memory at the cost of reallocationt time if more buffers are needed later. It has no effect on acquired Images, filled Images waiting to be acquired, or buffers being actively used by the source rendering to the Surface. Bug: 28695173 Change-Id: I427a8ba4ad73a267083f843dbf228bfc53a730d9