Move Line2DPathEffect (now Sk_) into a separate header file so it can
be shared and initialized.
Switch to the shared version in SampleAll and SampleSlides.
Remove the skip pipe flag from texteffects, since it can now be serialized.
I have a separate change to turn serialization on by default at https://codereview.appspot.com/6498121/
Review URL: https://codereview.appspot.com/6503106
git-svn-id: http://skia.googlecode.com/svn/trunk@5512 2bbb7eff-a529-9590-31e7-b0007b416f81