Update existing uses of /wd4267 to use the GN config

pdf/BUILD.gn

Index: pdf/BUILD.gn
diff --git a/pdf/BUILD.gn b/pdf/BUILD.gn
index 49f49a4048265df980b9791f0045047715fa615b..0f74323ff5702304429df57cf6a3bfd9a50d0b93 100644
--- a/pdf/BUILD.gn
+++ b/pdf/BUILD.gn
@@ -45,6 +45,9 @@ static_library("pdf") {
     "thumbnail_control.h",
   ]
 
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+
   if (pdf_engine == 0) {
     sources += [
       "pdfium/pdfium_api_string_buffer_adapter.cc",
@@ -63,10 +66,6 @@ static_library("pdf") {
     ]
   }
 
-  if (is_win) {
-    cflags = [ "/wd4267" ]  # TODO(jschuh) size_t to int truncations.
-  }
-
   deps = [
     "//base",
     "//components/ui/zoom:ui_zoom",