Bring pdfium file in sync with chrome, fix mac build

This permits PDFium to build on the Mac with Skia as the backend. It builds on Linux and Windows as well.

R=dsinclair@chromium.org,bungeman@google.com

Review-Url: https://codereview.chromium.org/1995003002
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index c5c2796..01acf58 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -330,11 +330,7 @@
       "//third_party/skia/src/ports/SkFontMgr_android_parser.cpp",
     ]
   }
-  if (!is_mac) {
-    sources -= [ "//third_party/skia/src/ports/SkFontHost_mac.cpp" ]
-  }
-
-  if (!is_linux && !is_android && !is_win) {
+  if (!is_linux && !is_android && !is_win && !is_mac) {
     sources -= [
       "//third_party/skia/src/ports/SkFontHost_FreeType.cpp",
       "//third_party/skia/src/ports/SkFontHost_FreeType_common.cpp",