A pair of NetLog changes for ongoing refactoring:

net/base/net_log.cc

Index: net/base/net_log.cc
===================================================================
--- net/base/net_log.cc	(revision 141814)
+++ net/base/net_log.cc	(working copy)
@@ -40,6 +40,8 @@
 
 Value* SourceEventParametersCallback(const NetLog::Source source,
                                      NetLog::LogLevel /* log_level */) {
+  if (!source.is_valid())
+    return NULL;
   DictionaryValue* event_params = new DictionaryValue();
   source.AddToEventParameters(event_params);
   return event_params;
@@ -61,6 +63,14 @@
   return event_params;
 }
 
+Value* NetLogString16Callback(const char* name,
+                              const string16* value,
+                              NetLog::LogLevel /* log_level */) {
+  DictionaryValue* event_params = new DictionaryValue();
+  event_params->SetString(name, *value);
+  return event_params;
+}
+
 }  // namespace
 
 Value* NetLog::Source::ToValue() const {
@@ -279,6 +289,13 @@
   return base::Bind(&NetLogStringCallback, name, value);
 }
 
+// static
+NetLog::ParametersCallback NetLog::StringCallback(const char* name,
+                                                  const string16* value) {
+  DCHECK(value);
+  return base::Bind(&NetLogString16Callback, name, value);
+}
+
 void NetLog::OnAddObserver(ThreadSafeObserver* observer, LogLevel log_level) {
   DCHECK(!observer->net_log_);
   observer->net_log_ = this;