Provide gtest printers for ui/gfx geometry types

ui/gfx/geometry/vector2d.h

Index: ui/gfx/geometry/vector2d.h
diff --git a/ui/gfx/geometry/vector2d.h b/ui/gfx/geometry/vector2d.h
index 12f29a956d77f19d3a9833b4cd914cb927ba6e36..4e404be1a7e2007702ec5a11e1358922bfa05f8d 100644
--- a/ui/gfx/geometry/vector2d.h
+++ b/ui/gfx/geometry/vector2d.h
@@ -10,6 +10,7 @@
 #ifndef UI_GFX_GEOMETRY_VECTOR2D_H_
 #define UI_GFX_GEOMETRY_VECTOR2D_H_
 
+#include <iosfwd>
 #include <string>
 
 #include "base/basictypes.h"
@@ -86,6 +87,11 @@ inline Vector2d operator-(const Vector2d& lhs, const Vector2d& rhs) {
   return result;
 }
 
+// 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 Vector2d& vector, ::std::ostream* os);
+
 }  // namespace gfx
 
 #endif // UI_GFX_GEOMETRY_VECTOR2D_H_