MR2 is going to be API 13.

Change-Id: I05b65ace073b8731e85b41ac4ae63e2745cb46b5

api/current.xml

@@ -143865,6 +143865,17 @@
  visibility="public"
 >
 </field>
+<field name="HONEYCOMB_MR2"
+ type="int"
+ transient="false"
+ volatile="false"
+ value="10000"
+ static="true"
+ final="true"
+ deprecated="not deprecated"
+ visibility="public"
+>
+</field>
 </class>
 <class name="Bundle"
  extends="java.lang.Object"

core/java/android/os/Build.java

@@ -227,9 +227,14 @@ public class Build {
         public static final int HONEYCOMB = 11;
         
         /**
-         * Newest version of Android, version 3.1.
+         * May 2011: Android 3.1.
          */
         public static final int HONEYCOMB_MR1 = 12;
+        
+        /**
+         * Current development version.
+         */
+        public static final int HONEYCOMB_MR2 = CUR_DEVELOPMENT;
     }
     
     /** The type of build, like "user" or "eng". */