There are only 2 language modes, not 3

src/code-stubs.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CODE_STUBS_H_
 #define V8_CODE_STUBS_H_
 
 #include "src/allocation.h"
 #include "src/assembler.h"
 #include "src/code-stub-assembler.h"
@@ skipping 1827 matching lines @@
   }
 
   int depth() const { return DepthBits::decode(minor_key_); }
   LanguageMode language_mode() const {
     return LanguageModeBits::decode(minor_key_);
   }
 
  private:
   class DepthBits : public BitField<int, 0, 4> {};
   STATIC_ASSERT(DepthBits::kMax == kMaximumDepth);
-  class LanguageModeBits : public BitField<LanguageMode, 4, 2> {};
-  STATIC_ASSERT(LANGUAGE_END == 3);
+  class LanguageModeBits : public BitField<LanguageMode, 4, 1> {};
+  STATIC_ASSERT(LANGUAGE_END == 2);
 
   DEFINE_CALL_INTERFACE_DESCRIPTOR(StoreGlobalViaContext);
   DEFINE_PLATFORM_CODE_STUB(StoreGlobalViaContext, PlatformCodeStub);
 };
 
 class CallApiCallbackStub : public PlatformCodeStub {
  public:
   static const int kArgBits = 3;
   static const int kArgMax = (1 << kArgBits) - 1;
 
@@ skipping 1350 matching lines @@
 #undef DEFINE_HYDROGEN_CODE_STUB
 #undef DEFINE_CODE_STUB
 #undef DEFINE_CODE_STUB_BASE
 
 extern Representation RepresentationFromType(Type* type);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CODE_STUBS_H_