Enable ES6 Symbols by default

test/cctest/test-heap-profiler.cc

 // Copyright 2011 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 454 matching lines @@
 
   const v8::HeapGraphNode* second_node =
       GetProperty(string_node, v8::HeapGraphEdge::kInternal, "second");
   CHECK_EQ(v8::HeapGraphNode::kString, second_node->GetType());
 
   heap_profiler->DeleteAllHeapSnapshots();
 }
 
 
 TEST(HeapSnapshotSymbol) {
-  i::FLAG_harmony_symbols = true;
-
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());
   v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
 
   CompileRun("a = Symbol('mySymbol');\n");
   const v8::HeapSnapshot* snapshot =
       heap_profiler->TakeHeapSnapshot(v8_str("Symbol"));
   CHECK(ValidateSnapshot(snapshot));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   const v8::HeapGraphNode* a =
@@ skipping 2276 matching lines @@
   map.AddRange(ToAddress(0x180), 0x80, 6U);
   map.AddRange(ToAddress(0x180), 0x80, 7U);
   CHECK_EQ(7, map.GetTraceNodeId(ToAddress(0x180)));
   CHECK_EQ(5, map.GetTraceNodeId(ToAddress(0x200)));
   CHECK_EQ(3, static_cast<int>(map.size()));
 
   map.Clear();
   CHECK_EQ(0, static_cast<int>(map.size()));
   CHECK_EQ(0, map.GetTraceNodeId(ToAddress(0x400)));
 }