Componentization: fix SupplementTracing<0>::~SupplementTracing<0>(void) already defined.

Source/platform/Supplementable.cpp

Index: Source/platform/Supplementable.cpp
diff --git a/Source/platform/Supplementable.cpp b/Source/platform/Supplementable.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..19b371a9a15487b562dbfe1a6724511acc706fa4
--- /dev/null
+++ b/Source/platform/Supplementable.cpp
@@ -0,0 +1,14 @@
+// Copyright 2015 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.
+
+#include "config.h"
+#include "platform/Supplementable.h"
+
+// This Supplementable.cpp, which includes only config.h and
+// Supplementable.h, should be in Source/platform,
+// because Supplementable is not compiled without this cpp.
+// So if we don't have this cpp, we will see unresolved symbol error
+// when constructor/destructor's address is required.
+// i.e. error LNK2005: "public: virtual __cdecl
+// blink::SupplementTracing<0>::~SupplementTracing<0>(void)"

[tasak, 2015/04/22 03:14:48]

To compile Supplementable.h, need this cpp file.
Without this cpp file, MSVC does not compile Supplementable.h with "class
__declspec(dllexport) SupplementTracing<false>".