[turbofan] Sanitize language mode for javascript operators.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index e8384722aef6a852546b4187803930e1b5d513aa..e71314f9c1af9558e6e249e16cdaab7dca870397 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -8,6 +8,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <ostream>
+
 #include "src/base/build_config.h"
 #include "src/base/logging.h"
 #include "src/base/macros.h"
@@ -238,6 +240,20 @@ enum LanguageMode {
 };
 
 
+inline std::ostream& operator<<(std::ostream& os, LanguageMode mode) {
+  switch (mode) {
+    case SLOPPY:
+      return os << "sloppy";
+    case STRICT:
+      return os << "strict";
+    case STRONG:
+      return os << "strong";
+    default:
+      return os << "unknown";
+  }
+}
+
+
 inline bool is_sloppy(LanguageMode language_mode) {
   return (language_mode & STRICT_BIT) == 0;
 }