Bring back OnBackPressedHandler

- Bring back OnBackPressedHandler so we can support lower version

TODO : Recreate OnBackAnimationCallback

src/com/android/launcher3/AbstractFloatingView.java

@@ -34,8 +34,6 @@ import android.view.View;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.view.animation.Interpolator;
 import android.widget.LinearLayout;
-import android.window.OnBackAnimationCallback;
-
 import androidx.annotation.IntDef;
 
 import com.android.launcher3.anim.PendingAnimation;
@@ -51,7 +49,7 @@ import java.lang.annotation.RetentionPolicy;
  */
 @TargetApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
 public abstract class AbstractFloatingView extends LinearLayout implements TouchController,
-        OnBackAnimationCallback {
+        OnBackPressedHandler {
 
     @IntDef(flag = true, value = {
             TYPE_COMPOSE_VIEW,