Different behavior of c++11 list-initialization

Please consider the following code:

class A {
private:
  std::string s;
public:
  A() = delete;
  A(const A&) = delete;
  A(A&&) = delete;
  A(const std::string &a) : s(a) {}
};

Now, I would like to initialize an array of A using list initialization. g++ (4.9.1) could successfully build the following code:

int main() {
  A arr[2] = {{"a"}, {"b"}};
  return 0;
}

But, it failed for the following code:

class Aggr {
private:
  A arr[2];
public:
  Aggr() : arr{{"a"}, {"b"}} {}
};

The error messages are,

test.cc: In constructor ‘Aggr::Aggr()’:
test.cc:22:28: error: use of deleted function ‘A::A(A&&)’
   Aggr() : arr{{"a"}, {"b"}} {}
                            ^          
test.cc:11:3: note: declared here
   A(A&&) = delete;
   ^

That said, a list-initializer tries to call a move constructor for initializing an array inside of a class. That code, however, was successfully built by clang v3.5 without any warnings. So, I would like to know what the C++11 (or later version) specifies rules with respect to list-initialization. Thanks in advance.