mojo: Add maps to java bindings.

mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java

Index: mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java
diff --git a/mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java b/mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java
index efb984264e7f9b5e910cb11f5a457187f0fe6f56..80ed9d1f20e76b1ea562796bfe97503f33390a6c 100644
--- a/mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java
+++ b/mojo/public/java/bindings/src/org/chromium/mojo/bindings/Decoder.java
@@ -145,6 +145,21 @@ public class Decoder {
     }
 
     /**
+     * Deserializes a {@link DataHeader} at the given offset and checks if it is correct for a map.
+     */
+    public void readDataHeaderForMap() {
+        DataHeader si = readDataHeader();
+        if (si.size != BindingsHelper.MAP_STRUCT_HEADER.size) {
+            throw new DeserializationException(
+                    "Incorrect header for map. The size is incorrect.");
+        }
+        if (si.numFields != BindingsHelper.MAP_STRUCT_HEADER.numFields) {
+            throw new DeserializationException(
+                    "Incorrect header for map. The number of fields is incorrect.");
+        }
+    }
+
+    /**
      * Deserializes a byte at the given offset.
      */
     public byte readByte(int offset) {