Update existing uses of /wd4267 to use the GN config

cc/BUILD.gn

Index: cc/BUILD.gn
diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index dafa89a13f1dce0ebebff797c4b4747584ec74f9..d3bc7619370d5a26006d72d75e43cd3280cf202e 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn
@@ -536,10 +536,8 @@ component("cc") {
     "trees/tree_synchronizer.h",
   ]
 
-  if (is_win) {
-    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    cflags = [ "/wd4267" ]  # size_t -> int
-  }
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   public_deps = [
     "//skia",
@@ -697,6 +695,8 @@ source_set("test_support") {
     "test/tiled_layer_test_common.h",
   ]
 
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+
   include_dirs = [
     ".",
     "test",