Add gfx::Insets::ToString().

app/gfx/insets.cc

Index: app/gfx/insets.cc
diff --git a/app/gfx/insets.cc b/app/gfx/insets.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7e3da0c166430f5274973e72fbed5616b4ee0731
--- /dev/null
+++ b/app/gfx/insets.cc
@@ -0,0 +1,16 @@
+// Copyright (c) 2009 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 "app/gfx/insets.h"
+
+#include "base/string_util.h"
+
+namespace gfx {
+
+std::string Insets::ToString() const {
+  // Print members in the same order of the constructor parameters.
+  return StringPrintf("%d,%d,%d,%d", top_,  left_, bottom_, right_);
+}
+
+}  // namespace gfx