Inserted a missing string encoding check in lastIndexOf.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 3ed6b523f0ead3b11453c4e36e0aa23c6b0c2511..e206bb9ac366f3ed1ade216406cf9914410b6ca0 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -13693,6 +13693,9 @@ THREADED_TEST(TwoByteStringInAsciiCons) {
       "str2;";
   Local<Value> result = CompileRun(init_code);
 
+  Local<Value> indexof = CompileRun("str2.indexOf('els')");
+  Local<Value> lastindexof = CompileRun("str2.lastIndexOf('dab')");
+
   CHECK(result->IsString());
   i::Handle<i::String> string = v8::Utils::OpenHandle(String::Cast(*result));
   int length = string->length();
@@ -13758,6 +13761,10 @@ THREADED_TEST(TwoByteStringInAsciiCons) {
 
   ExpectString("str2.charAt(2);", "e");
 
+  ExpectObject("str2.indexOf('els');", indexof);
+
+  ExpectObject("str2.lastIndexOf('dab');", lastindexof);
+
   reresult = CompileRun("str2.charCodeAt(2);");
   CHECK_EQ(static_cast<int32_t>('e'), reresult->Int32Value());
 }