[PDF] Add support for Clear, Src, Dst, DstOver xfermodes.

This uses the refactoring in http://codereview.appspot.com/4459041/ to add support for additional xfer modes.  Calling setupContentEntry may affect previous content entries (removing, reordering, or modifying their clip) and indicates to the caller if it should draw the new item or not.

Review URL: http://codereview.appspot.com/4464043

git-svn-id: http://skia.googlecode.com/svn/trunk@1271 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed