Add enable_ipc_logging build argument

ipc/BUILD.gn

Index: ipc/BUILD.gn
diff --git a/ipc/BUILD.gn b/ipc/BUILD.gn
index 16959fbaecb175d4ee670ca3923bbd50265354b3..db839a3717421f677e107f287384eca5b2204c6a 100644
--- a/ipc/BUILD.gn
+++ b/ipc/BUILD.gn
@@ -2,11 +2,23 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//build/config/nacl/config.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
 
+declare_args() {
+  # Enabling debug builds automatically sets enable_ipc_logging to true.
+  enable_ipc_logging = is_debug
+}
+
+buildflag_header("ipc_features") {
+  header = "ipc_features.h"
+
+  flags = [ "IPC_MESSAGE_LOG_ENABLED=$enable_ipc_logging" ]
+}
+
 component("ipc") {
   sources = [
     "export_template.h",
@@ -98,6 +110,7 @@ component("ipc") {
   defines = [ "IPC_IMPLEMENTATION" ]
 
   public_deps = [
+    ":ipc_features",
     ":mojom",
     ":param_traits",
     "//mojo/public/cpp/bindings",