HeapArray: Fix swap() not swapping size

Even though it's not used.

src/common/heap_array.h

@@ -247,7 +247,11 @@ class DynamicHeapArray
 
  void fill(const_reference value) { std::fill(begin(), end(), value); }
 
- void swap(this_type& move) { std::swap(m_data, move.m_data); }
+ void swap(this_type& rhs)
+ {
+ std::swap(m_data, rhs.m_data);
+ std::swap(m_size, rhs.m_size);
+ }
 
  void resize(size_t new_size) { internal_resize(new_size, m_data, m_size); }