Clarify docs around weak references to animator targets

package android.animation;

import android.annotation.Nullable;

import android.content.pm.ActivityInfo.Config;

import android.content.res.ConstantState;

     * operate on target objects (for example, {@link ValueAnimator}, but this method

     * is on the superclass for the convenience of dealing generically with those subclasses

     * that do handle targets.

     * <p>

     * <strong>Note:</strong> The target is stored as a weak reference internally to avoid leaking

     * resources by having animators directly reference old targets. Therefore, you should

     * ensure that animator targets always have a hard reference elsewhere.

     *

     * @param target The object being animated

     */

    public void setTarget(Object target) {

    public void setTarget(@Nullable Object target) {

    }

    // Hide reverse() and canReverse() for now since reverse() only work for simple

        return mTarget == null ? null : mTarget.get();

    }

    /**

     * Sets the target object whose property will be animated by this animation. If the

     * animator has been started, it will be canceled.

     *

     * @param target The object being animated

     */

    @Override

    public void setTarget(@Nullable Object target) {

        final Object oldTarget = getTarget();