Added focus behavior changes to Build.VERSION documentation.

Change-Id: I2c8f23f65ed6baabafd1a3a954be5f9f4341e2bc
diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 0541a53..7852125 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -757,6 +757,16 @@
 
         /**
          * O.
+         *
+         * <p>Applications targeting this or a later release will get these
+         * new changes in behavior:</p>
+         * <ul>
+         * <li>{@link android.R.attr#focusable} defaults to a new state ({@code auto}) where it will
+         * inherit the value of {@link android.R.attr#clickable} unless explicitly overridden.</li>
+         * <li>A default theme-appropriate focus-state highlight will be supplied to all Views
+         * which don't provide a focus-state drawable themselves. This can be disabled by setting
+         * {@link android.R.attr#defaultFocusHighlightEnabled} to false.</li>
+         * </ul>
          */
         public static final int O = 26;