Move CXFA_PDFFontMgr to CFGAS_PDFFontMgr

XFA bits passed into the PDFFontMgr are just used to get the
CPDF_Document and the CFGAS_FontMgr. This CL changes the code to pass
those two things into the constructor. Then, the fxfa/cxfa_pdffontmgr.*
code has been moved to fgas/cfgas_pdffontmgr.* to show it doesn't depend
on any of the XFA classes.

Change-Id: I21d791869e2a32ffedfd7c87bb3bbd035232d991
Reviewed-on: https://pdfium-review.googlesource.com/14550
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 2cf6552..aad97e9 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1488,6 +1488,8 @@
       "xfa/fgas/font/cfgas_fontmgr.h",
       "xfa/fgas/font/cfgas_gefont.cpp",
       "xfa/fgas/font/cfgas_gefont.h",
+      "xfa/fgas/font/cfgas_pdffontmgr.cpp",
+      "xfa/fgas/font/cfgas_pdffontmgr.h",
       "xfa/fgas/font/fgas_fontutils.cpp",
       "xfa/fgas/font/fgas_fontutils.h",
       "xfa/fgas/layout/cfx_break.cpp",
@@ -1690,8 +1692,6 @@
       "xfa/fxfa/cxfa_linkuserdata.h",
       "xfa/fxfa/cxfa_loadercontext.cpp",
       "xfa/fxfa/cxfa_loadercontext.h",
-      "xfa/fxfa/cxfa_pdffontmgr.cpp",
-      "xfa/fxfa/cxfa_pdffontmgr.h",
       "xfa/fxfa/cxfa_pieceline.cpp",
       "xfa/fxfa/cxfa_pieceline.h",
       "xfa/fxfa/cxfa_rendercontext.cpp",