Introduce {FAST,SLOW}_STRING_WRAPPER_ELEMENTS

src/crankshaft/mips/lithium-codegen-mips.cc

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index 04dedd6ec3b09a75090cc5f65781017cccd60826..7f14f1e23830c168a13ea1a2157bf07b818c85f2 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -2871,6 +2871,9 @@ void LCodeGen::DoLoadKeyedExternalArray(LLoadKeyed* instr) {
       case DICTIONARY_ELEMENTS:
       case FAST_SLOPPY_ARGUMENTS_ELEMENTS:
       case SLOW_SLOPPY_ARGUMENTS_ELEMENTS:
+      case FAST_STRING_WRAPPER_ELEMENTS:
+      case SLOW_STRING_WRAPPER_ELEMENTS:
+      case NO_ELEMENTS:
         UNREACHABLE();
         break;
     }
@@ -3973,6 +3976,9 @@ void LCodeGen::DoStoreKeyedExternalArray(LStoreKeyed* instr) {
       case DICTIONARY_ELEMENTS:
       case FAST_SLOPPY_ARGUMENTS_ELEMENTS:
       case SLOW_SLOPPY_ARGUMENTS_ELEMENTS:
+      case FAST_STRING_WRAPPER_ELEMENTS:
+      case SLOW_STRING_WRAPPER_ELEMENTS:
+      case NO_ELEMENTS:
         UNREACHABLE();
         break;
     }