Node_List inherits Node_Array, so it inherits uint Size() const.

To resolve naming conflict, Node_List uses size() (with little s) and keep Size() to return its capacity. I don't think it's a good practice to use capital initial to distinct two functions. In particular they have different meanings.

I'd hide name Size in Node_List. It turns out there are 4 instances does use Node_list::Size() and they are all legit.

* For target hotspot_variant-server_libjvm_gtest_objs_BUILD_GTEST_LIBJVM_link:
/local/home/xxinliu/Devel/jdk/src/hotspot/share/opto/loopnode.cpp:4471: error: undefined reference to ‘Node_List::Size() const’
/local/home/xxinliu/Devel/jdk/src/hotspot/share/opto/loopnode.cpp:4546: error: undefined reference to ‘Node_List::Size() const’
/local/home/xxinliu/Devel/jdk/src/hotspot/share/opto/loopnode.cpp:6359: error: undefined reference to ‘Node_List::Size() const’
/local/home/xxinliu/Devel/jdk/src/hotspot/share/opto/output.cpp:3075: error: undefined reference to ‘Node_List::Size() const’

One option is rename Node_Array::Size() to max(). this can avoid confusing names.
Alternatively, we could provide capacity() in Node_list and replace Node_List::Size() with it.