Provide gtest printers for ui/gfx geometry types

ui/gfx/geometry/box_f.h

Index: ui/gfx/geometry/box_f.h
diff --git a/ui/gfx/geometry/box_f.h b/ui/gfx/geometry/box_f.h
index 13fb9d0d47b62120848ab6efdf20126b75e50974..deb359abdd30ad8d513148ea9e3d10babdde46e9 100644
--- a/ui/gfx/geometry/box_f.h
+++ b/ui/gfx/geometry/box_f.h
@@ -5,6 +5,9 @@
 #ifndef UI_GFX_GEOMETRY_BOX_F_H_
 #define UI_GFX_GEOMETRY_BOX_F_H_
 
+#include <iosfwd>
+#include <string>
+
 #include "ui/gfx/geometry/point3_f.h"
 #include "ui/gfx/geometry/vector3d_f.h"
 
@@ -155,6 +158,11 @@ inline BoxF operator+(const BoxF& b, const Vector3dF& v) {
               b.depth());
 }
 
+// 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 BoxF& box, ::std::ostream* os);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_BOX_F_H_