message: Add a default constructor to Array4D
diff: @@ -54,6 +54,8 @@ namespace xla {
  template <typename T>
  class Array4D : public Array<T> {
  public:
  + Array4D() : Array<T>(std::vector<int64>{0, 0, 0, 0}) {}
  +
  // Creates a 4D array, uninitialized values.
  Array4D(int64 planes, int64 depth, int64 height, int64 width)
  : Array<T>(std::vector<int64>{planes, depth, height, width}) {}
  