@GuardedBy("mLock")
  private boolean maybeUpdateFileCacheSize() {
    long now = mClock.now();
    if ((!mCacheStats.isInitialized()) ||
        mCacheSizeLastUpdateTime == UNINITIALIZED ||
        (now - mCacheSizeLastUpdateTime) > FILECACHE_SIZE_UPDATE_PERIOD_MS) {
      return maybeUpdateFileCacheSizeAndIndex();
    }
    return false;
  }
@ GuardedBy ( "mLock" ) private boolean maybeUpdateFileCacheSize ( ) { long now = mClock . now ( ) ; if ( ( ! mCacheStats . isInitialized ( ) ) || mCacheSizeLastUpdateTime == UNINITIALIZED || ( now - mCacheSizeLastUpdateTime ) > FILECACHE_SIZE_UPDATE_PERIOD_MS ) { return maybeUpdateFileCacheSizeAndIndex ( ) ; } return false ; }
If file cache size is not calculated or if it was calculated
a long time ago (FILECACHE_SIZE_UPDATE_PERIOD_MS) recalculated from file listing.
@return true if it was recalculated, false otherwise.