Allow for no pdf rasterizers in gm.

Our poppler does not build properly with VS2013, but using
gyp_skia -Dskia_enable_poppler_enabled=0
also does not build due to kPDFRasterizers being statically empty.
This adds a do nothing, not run by default 'pdf rasterizer'.

R=epoger@google.com

Review URL: https://codereview.chromium.org/270263009

git-svn-id: http://skia.googlecode.com/svn/trunk@14676 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed