Introduce LanguageMode, drop StrictMode.

src/runtime/runtime-utils.h

Index: src/runtime/runtime-utils.h
diff --git a/src/runtime/runtime-utils.h b/src/runtime/runtime-utils.h
index 95d75f5084fb2348eabefd0b2b0fe62ffbfd1ffe..edddfca2d36ab874f722fdd7adbe30faa2a35872 100644
--- a/src/runtime/runtime-utils.h
+++ b/src/runtime/runtime-utils.h
@@ -70,13 +70,12 @@ namespace internal {
   PropertyDetails name = PropertyDetails(Smi::cast(args[index]));
 
 
-// Assert that the given argument has a valid value for a StrictMode
-// and store it in a StrictMode variable with the given name.
-#define CONVERT_STRICT_MODE_ARG_CHECKED(name, index) \
-  RUNTIME_ASSERT(args[index]->IsSmi());              \
-  RUNTIME_ASSERT(args.smi_at(index) == STRICT ||     \
-                 args.smi_at(index) == SLOPPY);      \
-  StrictMode name = static_cast<StrictMode>(args.smi_at(index));
+// Assert that the given argument has a valid value for a LanguageMode
+// and store it in a LanguageMode variable with the given name.
+#define CONVERT_LANGUAGE_MODE_ARG_CHECKED(name, index)        \
+  RUNTIME_ASSERT(args[index]->IsSmi());                       \
+  RUNTIME_ASSERT(is_valid_language_mode(args.smi_at(index))); \
+  LanguageMode name = static_cast<LanguageMode>(args.smi_at(index));
 
 
 // Assert that the given argument is a number within the Int32 range