Update existing uses of /wd4267 to use the GN config

tools/json_schema_compiler/test/BUILD.gn

Index: tools/json_schema_compiler/test/BUILD.gn
diff --git a/tools/json_schema_compiler/test/BUILD.gn b/tools/json_schema_compiler/test/BUILD.gn
index 76ae1b944495a533a757ca82b0541c074145ddfe..f91e69964ad7e1e43b064f9afb0e51321c2cb1b1 100644
--- a/tools/json_schema_compiler/test/BUILD.gn
+++ b/tools/json_schema_compiler/test/BUILD.gn
@@ -36,12 +36,11 @@ source_set("test") {
     "test_util.cc",
     "test_util.h",
   ]
+
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+
   public_deps = [
     ":api",
   ]
-
-  if (is_win) {
-    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    cflags = [ "/wd4267" ]
-  }
 }