Extracted NetLog class's inner enum types into their own enum classes and

net/log/net_log_source_type.h

Index: net/log/net_log_source_type.h
diff --git a/net/log/net_log_source_type.h b/net/log/net_log_source_type.h
new file mode 100644
index 0000000000000000000000000000000000000000..5c4950c2183a3ab800e7544da646f60379921d45
--- /dev/null
+++ b/net/log/net_log_source_type.h
@@ -0,0 +1,20 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_LOG_NET_LOG_SOURCE_TYPE_H_
+#define NET_LOG_NET_LOG_SOURCE_TYPE_H_
+
+namespace net {
+
+// The "source" identifies the entity that generated the log message.
+enum class NetLogSourceType {
+#define SOURCE_TYPE(label) label,
+#include "net/log/net_log_source_type_list.h"
+#undef SOURCE_TYPE
+  COUNT
+};
+
+}
+
+#endif  // NET_LOG_NET_LOG_SOURCE_TYPE_H_