Merge to XFA: Extern in .cpp files is a code smell, part 1.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 2277d5e8392e7b4e33e2be901010d00ad4d44253..d0030f42bcf3ceb27f3ab81a132609b7bc614715 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -308,6 +308,7 @@ static_library("fpdftext") {
     "core/src/fpdftext/txtproc.h",
     "core/src/fpdftext/unicodenormalization.cpp",
     "core/src/fpdftext/unicodenormalizationdata.cpp",
+    "core/src/fpdftext/unicodenormalizationdata.h",
   ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ ":pdfium_config", "//build/config/compiler:no_chromium_code" ]
@@ -514,6 +515,7 @@ static_library("fxge") {
     "core/src/fxge/dib/fx_dib_engine.cpp",
     "core/src/fxge/dib/fx_dib_main.cpp",
     "core/src/fxge/dib/fx_dib_transform.cpp",
+    "core/src/fxge/fontdata/chromefontdata/chromefontdata.h",
     "core/src/fxge/fontdata/chromefontdata/FoxitDingbats.c",
     "core/src/fxge/fontdata/chromefontdata/FoxitFixed.c",
     "core/src/fxge/fontdata/chromefontdata/FoxitFixedBold.c",