Create a subset of skia support for paths only

This is a continuation of https://codereview.chromium.org/2346483006/

This removes the need for agg, without providing
full Skia support.

It doesn't work yet, but it does compile and run
for simple PDFs.

R=dsinclair@google.com

Committed: https://pdfium.googlesource.com/pdfium/+/5d223298b26c9b2b6284cba9a51521d3873b6e58
Review-Url: https://codereview.chromium.org/2491693002
diff --git a/README.md b/README.md
index 98dbac7..c5fc651 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,7 @@
 is_debug = true  # Enable debugging features.
 
 pdf_use_skia = false  # Set true to enable experimental skia backend.
+pdf_use_skia_paths = false  # Set true to enable experimental skia backend (paths only).
 
 pdf_enable_xfa = true  # Set false to remove XFA support (implies JS support).
 pdf_enable_v8 = true  # Set false to remove Javascript support.