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

mojo/public/cpp/bindings/lib/array_internal.h

Index: mojo/public/cpp/bindings/lib/array_internal.h
diff --git a/mojo/public/cpp/bindings/lib/array_internal.h b/mojo/public/cpp/bindings/lib/array_internal.h
index c49409a3216e253646902887734194dba2025154..3681d8e6a4da50244f27c56f6a2d5ed5e284da65 100644
--- a/mojo/public/cpp/bindings/lib/array_internal.h
+++ b/mojo/public/cpp/bindings/lib/array_internal.h
@@ -451,6 +451,10 @@ template <typename T> struct ArrayTraits<T, false> {
   static inline void PushBack(std::vector<T>* vec, ForwardType value) {
     vec->push_back(value);
   }
+  static inline void Clone(const std::vector<T>& src_vec,
+                           std::vector<T>* dest_vec) {
+    dest_vec->assign(src_vec.begin(), src_vec.end());
+  }
 };
 
 template <typename T> struct ArrayTraits<T, true> {
@@ -499,6 +503,12 @@ template <typename T> struct ArrayTraits<T, true> {
     vec->swap(new_storage);
     Finalize(&new_storage);
   }
+  static inline void Clone(const std::vector<StorageType>& src_vec,
+                           std::vector<StorageType>* dest_vec) {
+    Resize(dest_vec, src_vec.size());
+    for (size_t i = 0; i < src_vec.size(); ++i)
+      at(dest_vec, i) = at(&src_vec, i).Clone();
+  }
 };
 
 template <> struct WrapperTraits<String, false> {