Provide gtest printers for ui/gfx geometry types

ui/gfx/geometry/vector2d_f.h

Index: ui/gfx/geometry/vector2d_f.h
diff --git a/ui/gfx/geometry/vector2d_f.h b/ui/gfx/geometry/vector2d_f.h
index 4bab99e5825048a6a8a06c62f470919a6b0e1ec2..593e7b82bdf81d6999868f7c08804a648e064ce4 100644
--- a/ui/gfx/geometry/vector2d_f.h
+++ b/ui/gfx/geometry/vector2d_f.h
@@ -10,6 +10,7 @@
 #ifndef UI_GFX_GEOMETRY_VECTOR2D_F_H_
 #define UI_GFX_GEOMETRY_VECTOR2D_F_H_
 
+#include <iosfwd>
 #include <string>
 
 #include "ui/gfx/gfx_export.h"
@@ -107,6 +108,11 @@ inline Vector2dF ScaleVector2d(const Vector2dF& v, float scale) {
   return ScaleVector2d(v, scale, scale);
 }
 
+// This is declared here for use in gtest-based unit tests but is defined in
+// the gfx_test_support target. Depend on that to use this in your unit test.
+// This should not be used in production code - call ToString() instead.
+void PrintTo(const Vector2dF& vector, ::std::ostream* os);
+
 }  // namespace gfx
 
 #endif // UI_GFX_GEOMETRY_VECTOR2D_F_H_