Move microtask queueing logic from JavaScript to C++

src/heap.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_HEAP_H_
 #define V8_HEAP_H_
 
 #include <cmath>
 
 #include "allocation.h"
@@ skipping 178 matching lines @@
   V(Symbol, frozen_symbol, FrozenSymbol)                                       \
   V(Symbol, nonexistent_symbol, NonExistentSymbol)                             \
   V(Symbol, elements_transition_symbol, ElementsTransitionSymbol)              \
   V(SeededNumberDictionary, empty_slow_element_dictionary,                     \
       EmptySlowElementDictionary)                                              \
   V(Symbol, observed_symbol, ObservedSymbol)                                   \
   V(Symbol, uninitialized_symbol, UninitializedSymbol)                         \
   V(Symbol, megamorphic_symbol, MegamorphicSymbol)                             \
   V(FixedArray, materialized_objects, MaterializedObjects)                     \
   V(FixedArray, allocation_sites_scratchpad, AllocationSitesScratchpad)        \
-  V(JSObject, microtask_state, MicrotaskState)
+  V(FixedArray, microtask_queue, MicrotaskQueue)
 
 // Entries in this list are limited to Smis and are not visited during GC.
 #define SMI_ROOT_LIST(V)                                                       \
   V(Smi, stack_limit, StackLimit)                                              \
   V(Smi, real_stack_limit, RealStackLimit)                                     \
   V(Smi, last_script_id, LastScriptId)                                         \
   V(Smi, arguments_adaptor_deopt_pc_offset, ArgumentsAdaptorDeoptPCOffset)     \
   V(Smi, construct_stub_deopt_pc_offset, ConstructStubDeoptPCOffset)           \
   V(Smi, getter_stub_deopt_pc_offset, GetterStubDeoptPCOffset)                 \
   V(Smi, setter_stub_deopt_pc_offset, SetterStubDeoptPCOffset)
@@ skipping 2608 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_