[compiler] Remove broken support for undetectable strings.

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/codegen.h"
@@ skipping 2855 matching lines @@
   // only has room for two bytes to hold a set of these types. :-P
   STATIC_ASSERT(NUMBER_OF_TYPES <= 16);
 
   class Types : public EnumSet<Type, uint16_t> {
    public:
     Types() : EnumSet<Type, uint16_t>(0) {}
     explicit Types(uint16_t bits) : EnumSet<Type, uint16_t>(bits) {}
 
     bool UpdateStatus(Handle<Object> object);
     bool NeedsMap() const;
-    bool CanBeUndetectable() const;
+    bool CanBeUndetectable() const {
+      return Contains(ToBooleanStub::SPEC_OBJECT);
+    }
     bool IsGeneric() const { return ToIntegral() == Generic().ToIntegral(); }
 
     static Types Generic() { return Types((1 << NUMBER_OF_TYPES) - 1); }
   };
 
   ToBooleanStub(Isolate* isolate, ResultMode mode, Types types = Types())
       : HydrogenCodeStub(isolate) {
     set_sub_minor_key(TypesBits::encode(types.ToIntegral()) |
                       ResultModeBits::encode(mode));
   }
@@ skipping 186 matching lines @@
 #undef DEFINE_PLATFORM_CODE_STUB
 #undef DEFINE_HANDLER_CODE_STUB
 #undef DEFINE_HYDROGEN_CODE_STUB
 #undef DEFINE_CODE_STUB
 #undef DEFINE_CODE_STUB_BASE
 
 extern Representation RepresentationFromType(Type* type);
 } }  // namespace v8::internal
 
 #endif  // V8_CODE_STUBS_H_