Unify geometry test printers in a test support target.

Source/platform/testing/GeometryPrinters.h

+// 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.
+
+#ifndef GeometryPrinters_h
+#define GeometryPrinters_h
+
+#include "platform/geometry/FloatRoundedRect.h"
+#include <iosfwd>
+
+namespace blink {
+
+class FloatBox;
+class FloatPoint;
+class FloatQuad;
+class FloatRect;
+class FloatSize;
+class LayoutRect;
+
+// GTest print support for geometry classes.
+//
+// To avoid ODR violations, these should also be declared in the respective
+// headers defining these types. This is required because otherwise a template
+// instantiation may be instantiated differently, depending on whether this
+// declaration is found.
+//
+// As a result, it is not necessary to include this file in tests in order to
+// use these printers. If, however, you get a link error about these symbols,
+// you need to make sure the blink_platform_test_support target is linked in
+// your unit test binary.
+void PrintTo(const FloatBox&, std::ostream*);
+void PrintTo(const FloatPoint&, std::ostream*);
+void PrintTo(const FloatQuad&, std::ostream*);
+void PrintTo(const FloatRect&, std::ostream*);
+void PrintTo(const FloatRoundedRect&, std::ostream*);
+void PrintTo(const FloatRoundedRect::Radii&, std::ostream*);
+void PrintTo(const FloatSize&, std::ostream*);
+void PrintTo(const LayoutRect&, std::ostream*);
+
+} // namespace blink
+
+#endif // GeometryPrinters_h