SkPDF: move all pdf sources into src/pdf

also, consolidate XPS backend into src/xps

remove from include/ almost always a good thing.
TBR=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1781773002
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac-Clang-x86_64-Release-CMake-Trybot

Review URL: https://codereview.chromium.org/1781773002
diff --git a/gyp/pdf.gypi b/gyp/pdf.gypi
index 888613e..af9a497 100644
--- a/gyp/pdf.gypi
+++ b/gyp/pdf.gypi
@@ -11,7 +11,6 @@
 #
 {
     'sources': [
-        '<(skia_src_path)/doc/SkDocument_PDF.cpp',
         '<(skia_src_path)/pdf/SkDeflate.cpp',
         '<(skia_src_path)/pdf/SkDeflate.h',
         '<(skia_src_path)/pdf/SkJpegInfo.cpp',
@@ -22,6 +21,8 @@
         '<(skia_src_path)/pdf/SkPDFCanon.h',
         '<(skia_src_path)/pdf/SkPDFDevice.cpp',
         '<(skia_src_path)/pdf/SkPDFDevice.h',
+        '<(skia_src_path)/pdf/SkPDFDocument.cpp',
+        '<(skia_src_path)/pdf/SkPDFDocument.h',
         '<(skia_src_path)/pdf/SkPDFFont.cpp',
         '<(skia_src_path)/pdf/SkPDFFont.h',
         '<(skia_src_path)/pdf/SkPDFFontImpl.h',