Update TextView ApiDocs.

Update/add ApiDocs for setText, BufferType, Editable.Factory and
Scannable.Factory.

Bug: 30670270
Bug: 30290798
Change-Id: I2ff1f79cfb4c0c3c955ce42326670cf266e1e404
diff --git a/core/java/android/text/Spannable.java b/core/java/android/text/Spannable.java
index ae5d356..39b78eb 100644
--- a/core/java/android/text/Spannable.java
+++ b/core/java/android/text/Spannable.java
@@ -46,15 +46,17 @@
     public void removeSpan(Object what);
 
     /**
-     * Factory used by TextView to create new Spannables.  You can subclass
-     * it to provide something other than SpannableString.
+     * Factory used by TextView to create new {@link Spannable Spannables}. You can subclass
+     * it to provide something other than {@link SpannableString}.
+     *
+     * @see android.widget.TextView#setSpannableFactory(Factory)
      */
     public static class Factory {
         private static Spannable.Factory sInstance = new Spannable.Factory();
 
         /**
          * Returns the standard Spannable Factory.
-         */ 
+         */
         public static Spannable.Factory getInstance() {
             return sInstance;
         }