Factory methods for heap-allocated SkImageFilter objects.
This is part of an effort to ensure that all SkPaint effects can only be
allocated on the heap.
This patch makes the constructors of SkImageFilter and its subclasses non-public
and instead provides factory methods for creating these objects on the heap. We
temporarily keep constructor of publicly visible classes public behind a flag.
BUG=skia:2187
R=scroggo@google.com, mtklein@chromium.org, reed@google.com, senorblanco@google.com, senorblanco@chromium.org, bsalomon@google.com, sugoi@chromium.org, zork@chromium.org
Author: dominikg@chromium.org
Review URL: https://codereview.chromium.org/182983003
git-svn-id: http://skia.googlecode.com/svn/trunk@13718 2bbb7eff-a529-9590-31e7-b0007b416f81
