Add serialization/deserialization of structs for mojo java bindings.

mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java

Index: mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
diff --git a/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java b/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
index f2aa0463e24578ee52439016367719908c7e02f6..0288678a022d342a8d085cfc14f6e25430a029c4 100644
--- a/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
+++ b/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
@@ -9,11 +9,23 @@ package org.chromium.mojo.bindings;
  */
 public class BindingsHelper {
     /**
-     * Alignment in byte for mojo serialization.
+     * Alignment in bytes for mojo serialization.
      */
     public static final int ALIGNMENT = 8;
 
     /**
+     * The size, in bytes, of a serialized handle. A handle is serialized as an int representing the
+     * offset of the handle in the list of handles.
+     */
+    public static final int SERIALIZED_HANDLE_SIZE = 4;
+
+    /**
+     * The size, in bytes, of a serialized pointer. A pointer is serializaed as an unsigned long
+     * representing the offset from its position to the pointed elemnt.
+     */
+    public static final int POINTER_SIZE = 8;
+
+    /**
      * Align |size| on {@link BindingsHelper#ALIGNMENT}.
      */
     public static int align(int size) {