ES6 symbols: turn symbols into a proper primitive type

src/runtime.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 5017 matching lines @@
       if (heap_obj->IsTrue() || heap_obj->IsFalse()) {
         return isolate->heap()->boolean_string();
       }
       if (heap_obj->IsNull()) {
         return FLAG_harmony_typeof
             ? isolate->heap()->null_string()
             : isolate->heap()->object_string();
       }
       ASSERT(heap_obj->IsUndefined());
       return isolate->heap()->undefined_string();
+    case SYMBOL_TYPE:
+      return isolate->heap()->symbol_string();
     case JS_FUNCTION_TYPE:
     case JS_FUNCTION_PROXY_TYPE:
       return isolate->heap()->function_string();
     default:
       // For any kind of object not handled above, the spec rule for
       // host objects gives that it is okay to return "object"
       return isolate->heap()->object_string();
   }
 }
 
@@ skipping 8357 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal