Upgrade Symbol implementation to match current ES6 behavior.

test/cctest/test-api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2769 matching lines @@
   v8::Local<v8::Value> sym_val = sym2;
   CHECK(sym_val->IsSymbol());
   CHECK(sym_val->Equals(sym2));
   CHECK(sym_val->StrictEquals(sym2));
   CHECK(v8::Symbol::Cast(*sym_val)->Equals(sym2));
 
   v8::Local<v8::Value> sym_obj = v8::SymbolObject::New(isolate, sym2);
   CHECK(sym_obj->IsSymbolObject());
   CHECK(!sym2->IsSymbolObject());
   CHECK(!obj->IsSymbolObject());
-  CHECK(sym_obj->Equals(sym2));
+  // Comparing Symbol wrapper with Symbol will throw when
+  // ToPrimitive() is attempted performed on the wrapper.
+  {
+    v8::TryCatch try_catch;
+    sym_obj->Equals(sym2);
+    CHECK(try_catch.HasCaught());
+  }
   CHECK(!sym_obj->StrictEquals(sym2));
   CHECK(v8::SymbolObject::Cast(*sym_obj)->Equals(sym_obj));
   CHECK(v8::SymbolObject::Cast(*sym_obj)->ValueOf()->Equals(sym2));
 
   // Make sure delete of a non-existent symbol property works.
   CHECK(obj->Delete(sym1));
   CHECK(!obj->Has(sym1));
 
   CHECK(obj->Set(sym1, v8::Integer::New(isolate, 1503)));
   CHECK(obj->Has(sym1));
@@ skipping 19176 matching lines @@
 
 
 TEST(TestFunctionCallOptimization) {
   i::FLAG_allow_natives_syntax = true;
   ApiCallOptimizationChecker checker;
   checker.Run(true, true);
   checker.Run(false, true);
   checker.Run(true, false);
   checker.Run(false, false);
 }