USHORT_MAX is not yet defined in the MinGW version of intsafe.h that we use.

diff --git a/base/win/win_util.cc b/base/win/win_util.cc
index f9f87fc61303..a3308c3c4013 100644
--- a/base/win/win_util.cc
+++ b/base/win/win_util.cc
@@ -96,6 +96,10 @@
 #else
 #include <intsafe.h>
 #include <processthreadsapi.h>
+#if defined(__MINGW32__)
+// Not defined yet in version of MinGW we use.
+#define USHORT_MAX 65535
+#endif  // defined(__MINGW32__)
 #endif  // !defined(MOZ_SANDBOX)

 namespace base {