linux plugins: eliminate GtkWidget* from plugin process

chrome/common/ipc_message_utils.h

Index: chrome/common/ipc_message_utils.h
diff --git a/chrome/common/ipc_message_utils.h b/chrome/common/ipc_message_utils.h
index 2ae2ab5cdbd4b244250f3720befd71cc9585c063..f777d06c8728a09c97ce904deffc9496650f9394 100644
--- a/chrome/common/ipc_message_utils.h
+++ b/chrome/common/ipc_message_utils.h
@@ -176,6 +176,27 @@ struct ParamTraits<long> {
   }
 };
 
+#if defined(OS_LINUX)
+// unsigned long is used for serializing X window ids.
+template <>
+struct ParamTraits<unsigned long> {
+  typedef unsigned long param_type;
+  static void Write(Message* m, const param_type& p) {
+    m->WriteLong(p);
+  }
+  static bool Read(const Message* m, void** iter, param_type* r) {
+    long read_output;
+    if (!m->ReadLong(iter, &read_output))
+      return false;
+    *r = static_cast<unsigned long>(read_output);
+    return true;
+  }
+  static void Log(const param_type& p, std::wstring* l) {
+    l->append(StringPrintf(L"%ul", p));
+  }
+};
+#endif
+
 template <>
 struct ParamTraits<size_t> {
   typedef size_t param_type;