Provide gtest printers for ui/gfx geometry types

ui/gfx/geometry/size.h

Index: ui/gfx/geometry/size.h
diff --git a/ui/gfx/geometry/size.h b/ui/gfx/geometry/size.h
index 78984b073f493336b03712db46f1a3a53338261a..5040a013503783132653e7c12df0e06448a5165b 100644
--- a/ui/gfx/geometry/size.h
+++ b/ui/gfx/geometry/size.h
@@ -5,6 +5,7 @@
 #ifndef UI_GFX_GEOMETRY_SIZE_H_
 #define UI_GFX_GEOMETRY_SIZE_H_
 
+#include <iosfwd>
 #include <string>
 
 #include "base/compiler_specific.h"
@@ -62,6 +63,11 @@ inline bool operator!=(const Size& lhs, const Size& rhs) {
 extern template class SizeBase<Size, int>;
 #endif
 
+// 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 Size& size, ::std::ostream* os);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_SIZE_H_