Refactor CFX_BasicArray.

The |nGrowBy| argument to |SetSize| was always -1, which caused the
effective m_nGrowBy value to always be its default value: 0. So it was not
needed, and was cluttering up the logic.

BUG=384662

Check for integer overflow in CFX_BasicArray.

BUG=384662
R=bo_xu@foxitsoftware.com, rsesek@chromium.org

Review URL: https://codereview.chromium.org/415803002