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diff --git a/deps/v8/src/parsing/preparse-data-impl.h b/deps/v8/src/parsing/preparse-data-impl.h
new file mode 100644
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--- /dev/null
+++ b/deps/v8/src/parsing/preparse-data-impl.h
@@ -0,0 +1,234 @@
+// Copyright 2018 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_PARSING_PREPARSE_DATA_IMPL_H_
+#define V8_PARSING_PREPARSE_DATA_IMPL_H_
+
+#include "src/parsing/preparse-data.h"
+
+#include "src/assert-scope.h"
+
+namespace v8 {
+namespace internal {
+
+// Classes which are internal to prepared-scope-data.cc, but are exposed in
+// a header for tests.
+
+// Wraps a ZoneVector<uint8_t> to have with functions named the same as
+// PodArray<uint8_t>.
+class ZoneVectorWrapper {
+ public:
+  ZoneVectorWrapper() = default;
+  explicit ZoneVectorWrapper(ZoneVector<uint8_t>* data) : data_(data) {}
+
+  int data_length() const { return static_cast<int>(data_->size()); }
+
+  uint8_t get(int index) const { return data_->at(index); }
+
+ private:
+  ZoneVector<uint8_t>* data_ = nullptr;
+};
+
+template <class Data>
+class BaseConsumedPreparseData : public ConsumedPreparseData {
+ public:
+  class ByteData : public PreparseByteDataConstants {
+   public:
+    ByteData() {}
+
+    // Reading from the ByteData is only allowed when a ReadingScope is on the
+    // stack. This ensures that we have a DisallowHeapAllocation in place
+    // whenever ByteData holds a raw pointer into the heap.
+    class ReadingScope {
+     public:
+      ReadingScope(ByteData* consumed_data, Data data)
+          : consumed_data_(consumed_data) {
+        consumed_data->data_ = data;
+#ifdef DEBUG
+        consumed_data->has_data_ = true;
+#endif
+      }
+      explicit ReadingScope(BaseConsumedPreparseData<Data>* parent)
+          : ReadingScope(parent->scope_data_.get(), parent->GetScopeData()) {}
+      ~ReadingScope() {
+#ifdef DEBUG
+        consumed_data_->has_data_ = false;
+#endif
+      }
+
+     private:
+      ByteData* consumed_data_;
+      DISALLOW_HEAP_ALLOCATION(no_gc);
+    };
+
+    void SetPosition(int position) {
+      DCHECK_LE(position, data_.data_length());
+      index_ = position;
+    }
+
+    size_t RemainingBytes() const {
+      DCHECK(has_data_);
+      DCHECK_LE(index_, data_.data_length());
+      return data_.data_length() - index_;
+    }
+
+    bool HasRemainingBytes(size_t bytes) const {
+      DCHECK(has_data_);
+      return index_ <= data_.data_length() && bytes <= RemainingBytes();
+    }
+
+    int32_t ReadUint32() {
+      DCHECK(has_data_);
+      DCHECK(HasRemainingBytes(kUint32Size));
+      // Check that there indeed is an integer following.
+      DCHECK_EQ(data_.get(index_++), kUint32Size);
+      int32_t result = data_.get(index_) + (data_.get(index_ + 1) << 8) +
+                       (data_.get(index_ + 2) << 16) +
+                       (data_.get(index_ + 3) << 24);
+      index_ += 4;
+      stored_quarters_ = 0;
+      return result;
+    }
+
+    int32_t ReadVarint32() {
+      DCHECK(HasRemainingBytes(kVarintMinSize));
+      DCHECK_EQ(data_.get(index_++), kVarintMinSize);
+      int32_t value = 0;
+      bool has_another_byte;
+      unsigned shift = 0;
+      do {
+        uint8_t byte = data_.get(index_++);
+        value |= static_cast<int32_t>(byte & 0x7F) << shift;
+        shift += 7;
+        has_another_byte = byte & 0x80;
+      } while (has_another_byte);
+      DCHECK_EQ(data_.get(index_++), kVarintEndMarker);
+      stored_quarters_ = 0;
+      return value;
+    }
+
+    uint8_t ReadUint8() {
+      DCHECK(has_data_);
+      DCHECK(HasRemainingBytes(kUint8Size));
+      // Check that there indeed is a byte following.
+      DCHECK_EQ(data_.get(index_++), kUint8Size);
+      stored_quarters_ = 0;
+      return data_.get(index_++);
+    }
+
+    uint8_t ReadQuarter() {
+      DCHECK(has_data_);
+      if (stored_quarters_ == 0) {
+        DCHECK(HasRemainingBytes(kUint8Size));
+        // Check that there indeed are quarters following.
+        DCHECK_EQ(data_.get(index_++), kQuarterMarker);
+        stored_byte_ = data_.get(index_++);
+        stored_quarters_ = 4;
+      }
+      // Read the first 2 bits from stored_byte_.
+      uint8_t result = (stored_byte_ >> 6) & 3;
+      DCHECK_LE(result, 3);
+      --stored_quarters_;
+      stored_byte_ <<= 2;
+      return result;
+    }
+
+   private:
+    Data data_ = {};
+    int index_ = 0;
+    uint8_t stored_quarters_ = 0;
+    uint8_t stored_byte_ = 0;
+#ifdef DEBUG
+    bool has_data_ = false;
+#endif
+  };
+
+  BaseConsumedPreparseData() : scope_data_(new ByteData()), child_index_(0) {}
+
+  virtual Data GetScopeData() = 0;
+
+  virtual ProducedPreparseData* GetChildData(Zone* zone, int child_index) = 0;
+
+  ProducedPreparseData* GetDataForSkippableFunction(
+      Zone* zone, int start_position, int* end_position, int* num_parameters,
+      int* num_inner_functions, bool* uses_super_property,
+      LanguageMode* language_mode) final;
+
+  void RestoreScopeAllocationData(DeclarationScope* scope) final;
+
+#ifdef DEBUG
+  bool VerifyDataStart();
+#endif
+
+ private:
+  void RestoreDataForScope(Scope* scope);
+  void RestoreDataForVariable(Variable* var);
+  void RestoreDataForInnerScopes(Scope* scope);
+
+  std::unique_ptr<ByteData> scope_data_;
+  // When consuming the data, these indexes point to the data we're going to
+  // consume next.
+  int child_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(BaseConsumedPreparseData);
+};
+
+// Implementation of ConsumedPreparseData for on-heap data.
+class OnHeapConsumedPreparseData final
+    : public BaseConsumedPreparseData<PreparseData> {
+ public:
+  OnHeapConsumedPreparseData(Isolate* isolate, Handle<PreparseData> data);
+
+  PreparseData GetScopeData() final;
+  ProducedPreparseData* GetChildData(Zone* zone, int child_index) final;
+
+ private:
+  Isolate* isolate_;
+  Handle<PreparseData> data_;
+};
+
+// A serialized PreparseData in zone memory (as apposed to being on-heap).
+class ZonePreparseData : public ZoneObject {
+ public:
+  ZonePreparseData(Zone* zone, Vector<uint8_t>* byte_data, int child_length);
+
+  Handle<PreparseData> Serialize(Isolate* isolate);
+
+  int children_length() const { return static_cast<int>(children_.size()); }
+
+  ZonePreparseData* get_child(int index) { return children_[index]; }
+
+  void set_child(int index, ZonePreparseData* child) {
+    DCHECK_NOT_NULL(child);
+    children_[index] = child;
+  }
+
+  ZoneVector<uint8_t>* byte_data() { return &byte_data_; }
+
+ private:
+  ZoneVector<uint8_t> byte_data_;
+  ZoneVector<ZonePreparseData*> children_;
+
+  DISALLOW_COPY_AND_ASSIGN(ZonePreparseData);
+};
+
+// Implementation of ConsumedPreparseData for PreparseData
+// serialized into zone memory.
+class ZoneConsumedPreparseData final
+    : public BaseConsumedPreparseData<ZoneVectorWrapper> {
+ public:
+  ZoneConsumedPreparseData(Zone* zone, ZonePreparseData* data);
+
+  ZoneVectorWrapper GetScopeData() final;
+  ProducedPreparseData* GetChildData(Zone* zone, int child_index) final;
+
+ private:
+  ZonePreparseData* data_;
+  ZoneVectorWrapper scope_data_wrapper_;
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_PARSING_PREPARSE_DATA_IMPL_H_