Rename png_ functions conflicting with chrome.

third_party/BUILD.gn

Index: third_party/BUILD.gn
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index 92fbcaa9fb88e575bbef28d13eb94de319b07374..ec6f8cb7f83574c8acc3cff784251258ee98f5a1 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -298,6 +298,7 @@ source_set("fx_lpng") {
     "libpng16/pnglibconf.h",
     "libpng16/pngmem.c",
     "libpng16/pngpread.c",
+    "libpng16/pngprefix.h",
     "libpng16/pngpriv.h",
     "libpng16/pngread.c",
     "libpng16/pngrio.c",
@@ -320,10 +321,10 @@ if (pdf_enable_xfa) {
       "//build/config/compiler:no_chromium_code",
       "//third_party/pdfium:pdfium_config",
     ]
-    deps = [ "//third_party:jpeg" ]
+    deps = [
+      "//third_party:jpeg",
+    ]
     sources = [
-      "libtiff/tiffiop.h",
-      "libtiff/tiffvers.h",
       "libtiff/tif_aux.c",
       "libtiff/tif_close.c",
       "libtiff/tif_codec.c",
@@ -359,6 +360,8 @@ if (pdf_enable_xfa) {
       "libtiff/tif_warning.c",
       "libtiff/tif_write.c",
       "libtiff/tif_zip.c",
+      "libtiff/tiffiop.h",
+      "libtiff/tiffvers.h",
     ]
   }
 }