Clarify hasSelection description

It's unintuitive that hasSelection() can return false, while
getSelectionStart() and getSelectionEnd() return meaningful non -1
values.

Test: TreeHugger

Change-Id: Iea2157f4b3b2c13c74547ba31eb4131496f939cc

core/java/android/widget/TextView.java

@@ -9420,7 +9420,7 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
     }
 
     /**
-     * Return true iff there is a selection inside this text view.
+     * Return true iff there is a selection of nonzero length inside this text view.
      */
     public boolean hasSelection() {
         final int selectionStart = getSelectionStart();