8252546: Move ObservableValue's equality check and lazy evaluation descriptions to @implSpec

modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java

@@ -39,13 +39,11 @@
  * <p>
  * An implementation of {@code ObservableValue} may support lazy evaluation,
  * which means that the value is not immediately recomputed after changes, but
- * lazily the next time the value is requested. All bindings and properties in
- * this library support lazy evaluation.
+ * lazily the next time the value is requested (see note 1 in "Implementation Requirements").
  * <p>
  * An {@code ObservableValue} generates two types of events: change events and
- * invalidation events. A change event indicates that the value has changed.
- * Current implementing classes in JavaFX check for a change using reference
- * equality (and not object equality, {@code Object#equals(Object)}) of the value. An
+ * invalidation events. A change event indicates that the value has changed
+ * (see note 2 in "Implementation Requirements"). An
  * invalidation event is generated if the current value is not valid anymore.
  * This distinction becomes important if the {@code ObservableValue} supports
  * lazy evaluation, because for a lazily evaluated value one does not know if an
@@ -70,6 +68,12 @@
  * @param <T>
  *            The type of the wrapped value.
  *
+ * @implSpec <ol>
+ * <li> All bindings and properties in the JavaFX library support lazy evaluation.</li>
+ * <li> All implementing classes in the JavaFX library check for a change using reference
+ * equality (and not object equality, {@code Object#equals(Object)}) of the value.</li>
+ * </ol>
+ *
  * @see ObservableBooleanValue
  * @see ObservableDoubleValue
  * @see ObservableFloatValue