Unify geometry test printers in a test support target.

Source/platform/geometry/LayoutRect.h

Index: Source/platform/geometry/LayoutRect.h
diff --git a/Source/platform/geometry/LayoutRect.h b/Source/platform/geometry/LayoutRect.h
index bfe86fc69df82597a74d943458c7383b035a559e..7854cba0e38329ba678f01fd392604a0cd9c5344 100644
--- a/Source/platform/geometry/LayoutRect.h
+++ b/Source/platform/geometry/LayoutRect.h
@@ -35,6 +35,7 @@
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/geometry/LayoutRectOutsets.h"
 #include "wtf/Vector.h"
+#include <iosfwd>
 
 namespace blink {
 
@@ -251,6 +252,10 @@ inline IntRect pixelSnappedIntRect(LayoutPoint location, LayoutSize size)
     return IntRect(roundedIntPoint(location), pixelSnappedIntSize(size, location));
 }
 
+// Redeclared here to avoid ODR issues.
+// See platform/testing/GeometryPrinters.h.
+void PrintTo(const LayoutRect&, std::ostream*);
+
 } // namespace blink
 
 #endif // LayoutRect_h