Mojo cpp bindings: support Clone() for structs and arrays which don't contain handles.

mojo/public/cpp/bindings/array.h

Index: mojo/public/cpp/bindings/array.h
diff --git a/mojo/public/cpp/bindings/array.h b/mojo/public/cpp/bindings/array.h
index 0ef62619439c7e03642eb1805f3de9d52c212c4b..53c8c1842dda113d84efc592e95c05e9e19900be 100644
--- a/mojo/public/cpp/bindings/array.h
+++ b/mojo/public/cpp/bindings/array.h
@@ -105,6 +105,16 @@ class Array {
     vec_.swap(*other);
   }
 
+  // Please note that calling this method will fail compilation if the element
+  // type cannot be cloned (which usually means that it is a Mojo handle type or
+  // a type contains Mojo handles).
+  Array Clone() const {
+    Array result;
+    result.is_null_ = is_null_;
+    Traits::Clone(vec_, &result.vec_);
+    return result.Pass();
+  }
+
  private:
   typedef std::vector<StorageType> Array::*Testable;