Migrate the id property to the base class internals
so that pimpl classes could access the data easier.
This is a sort of prerequisite change for the coming texmap anti-aliasing.
removed invalid nullptr checks.
New allocation doesn't gurantee that returns nullptr when it's failed.
It's useless on the modern compliers and our policy respects it.
we should avoid code insertion during file dependencies,
such as #include "xxx.h" which has implementations.
This could increase binary size, we can avoid it as possible.
Current patch improves binary size like this:
From: file(2059008) = text(120360) data(8096) bss(80) dec(128536)
To : file(1921832) = text(118429) data(7872) bss(56) dec(126357)
More additional patches will come in to optmize binary size.
