synchronized boolean decrementUsageCount(@NotNull VirtualFilePointerImpl pointer) {
    boolean shouldKill = pointer.incrementUsageCount(-1) == 0;
    if (!shouldKill) {
      return false;
    }
    getRoot(pointer.myNode.myFS).removePointer(pointer);
    pointer.myNode = null;
    assertConsistency();
    myPointerSetModCount++;
    return true;
  }
synchronized boolean decrementUsageCount(@NotNull VirtualFilePointerImpl pointer)