code: public synchronized void setAutoShutdownEnabled(boolean enabled) {
          try {
              if (mShutdownHook == null) {
                  if (enabled) {
                      ShutdownHook hook = new ShutdownHook(this);
                      Runtime.getRuntime().addShutdownHook(hook);
                      mShutdownHook = hook;
                  }
              } else {
                  if (!enabled) {
                      Runtime.getRuntime().removeShutdownHook(mShutdownHook);
                      mShutdownHook = null;
                  }
              }
          } catch (IllegalStateException e) {
              // Shutdown is in progress so make no changes.
          }
      }
docs: Required by ShutdownCapability.