Fix memory corruption bug in LookupKey::FromLookupKey().
Fix memory corruption bug in LookupKey::FromLookupKey().

Copy nodes_ only if other object is a different object.

R=rouslan@chromium.org
BUG=

Review URL: https://codereview.appspot.com/117950046

parastoog/my-libaddressinput,google/libaddressinput,googlei18n/libaddressinput,dlyongemallo/libaddressinput,mcanthony/libaddressinput,roubert/libaddressinput,dlyongemallo/libaddressinput,mcanthony/libaddressinput,parastoog/my-libaddressinput,googlei18n/libaddressinput,parastoog/my-libaddressinput,googlei18n/libaddressinput,google/libaddressinput,dlyongemallo/libaddressinput,google/libaddressinput,roubert/libaddressinput,mcanthony/libaddressinput,roubert/libaddressinput