Implement cc::FilterOperation StructTraits

mojo/public/cpp/bindings/array_traits_carray.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_CARRAY_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_CARRAY_H_
 
 #include <vector>
 
 #include "mojo/public/cpp/bindings/array_traits.h"
 
 namespace mojo {
 
 template <typename T>
 struct CArray {
   CArray() : size(0), max_size(0), data(nullptr) {}
   explicit CArray(size_t max_size)
       : size(0), max_size(max_size), data(nullptr) {}
   CArray(size_t size, size_t max_size, T* data)
       : size(size), max_size(max_size), data(data) {}
   size_t size;
   size_t max_size;
   T* data;
 };
 
 template <typename T>
 struct ArrayTraits<CArray<T>> {
   using Element = T;
 
+  static bool IsNull(const CArray<T>& input) { return !input.data; }
+
   static size_t GetSize(const CArray<T>& input) { return input.size; }
 
   static T* GetData(CArray<T>& input) { return input.data; }
 
   static const T* GetData(const CArray<T>& input) { return input.data; }
 
   static T& GetAt(CArray<T>& input, size_t index) { return input.data[index]; }
 
   static const T& GetAt(const CArray<T>& input, size_t index) {
     return input.data[index];
   }
 
   static bool Resize(CArray<T>& input, size_t size) {
     if (size > input.max_size)
       return false;
 
     input.size = size;
     return true;
   }
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_CARRAY_H_