ES6 symbols: Implement Symbol intrinsic and basic functionality

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 661 matching lines @@
     isolate->counters()->cow_arrays_created_runtime()->Increment();
   }
 
   JSObject* boilerplate_object = JSObject::cast(*boilerplate);
   AllocationSiteMode mode = AllocationSiteInfo::GetMode(
       boilerplate_object->GetElementsKind());
   return isolate->heap()->CopyJSObject(boilerplate_object, mode);
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateSymbol) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 0);
+  return isolate->heap()->AllocateSymbol();
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateJSProxy) {
   ASSERT(args.length() == 2);
   CONVERT_ARG_CHECKED(JSReceiver, handler, 0);
   Object* prototype = args[1];
   Object* used_prototype =
       prototype->IsJSReceiver() ? prototype : isolate->heap()->null_value();
   return isolate->heap()->AllocateJSProxy(handler, used_prototype);
 }
 
 
@@ skipping 12836 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