[compiler] Remove broken support for undetectable strings.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 5e2c4e76b408afea089282f4cd13020d8dd8bb01..b48b828ae7f336643e9c4d8886fb7ba4f7277177 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -1013,12 +1013,6 @@ bool ToBooleanStub::Types::NeedsMap() const {
 }
 
 
-bool ToBooleanStub::Types::CanBeUndetectable() const {
-  return Contains(ToBooleanStub::SPEC_OBJECT)
-      || Contains(ToBooleanStub::STRING);
-}
-
-
 void StubFailureTrampolineStub::GenerateAheadOfTime(Isolate* isolate) {
   StubFailureTrampolineStub stub1(isolate, NOT_JS_FUNCTION_STUB_MODE);
   StubFailureTrampolineStub stub2(isolate, JS_FUNCTION_STUB_MODE);