Canvas::clear() introduces a new argument "free" that deterimes freeing the retained paints.
If free is true, Canvas won't delete the retained paints so that user keep paints valid.
In this scenario, user must have paints pointers, free them manually or push them again to the canvas.
This scenario is useful if user wants to re-organize paints order in the list or reuse them.
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.
remove unnecessary condition.
implementation won't be included multiple times not like headers.
Thus this condition is unnecessary.
Change-Id: Id37e675c40ce7213a06c950da8e5ca17ff7245c9
