Add an experimental public API for value serialization.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index d7e39adbaee34955ce14737573d2ca6fb1fb5458..968df4b7ce77062f52ca799f55f02f8a5dc34dc4 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1664,6 +1664,91 @@ class V8_EXPORT JSON {
       Local<String> gap = Local<String>());
 };
 
+/**
+ * Value serialization compatible with the HTML structured clone algorithm.
+ * The format is backward-compatible (i.e. safe to store to disk).
+ *
+ * WARNING: This API is under development, and changes (including incompatible
+ * changes to the API or wire format) may occur without notice until this
+ * warning is removed.
+ */
+class V8_EXPORT ValueSerializer {
+ public:
+  explicit ValueSerializer(Isolate* isolate);
+  ~ValueSerializer();
+
+  /*
+   * Writes out a header, which includes the format version.
+   */
+  void WriteHeader();
+
+  /*
+   * Serializes a JavaScript value into the buffer.
+   */
+  V8_WARN_UNUSED_RESULT Maybe<bool> WriteValue(Local<Context> context,
+                                               Local<Value> value);
+
+  /*
+   * Returns the stored data. This serializer should not be used once the buffer
+   * is released. The contents are undefined if a previous write has failed.
+   */
+  std::vector<uint8_t> ReleaseBuffer();
+
+ private:
+  ValueSerializer(const ValueSerializer&) = delete;
+  void operator=(const ValueSerializer&) = delete;
+
+  struct PrivateData;
+  PrivateData* private_;
+};
+
+/**
+ * Deserializes values from data written with ValueSerializer, or a compatible
+ * implementation.
+ *
+ * WARNING: This API is under development, and changes (including incompatible
+ * changes to the API or wire format) may occur without notice until this
+ * warning is removed.
+ */
+class V8_EXPORT ValueDeserializer {
+ public:
+  ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size);
+  ~ValueDeserializer();
+
+  /*
+   * Reads and validates a header (including the format version).
+   * May, for example, reject an invalid or unsupported wire format.
+   */
+  V8_WARN_UNUSED_RESULT Maybe<bool> ReadHeader();
+
+  /*
+   * Deserializes a JavaScript value from the buffer.
+   */
+  V8_WARN_UNUSED_RESULT MaybeLocal<Value> ReadValue(Local<Context> context);
+
+  /*
+   * Must be called before ReadHeader to enable support for reading the legacy
+   * wire format (i.e., which predates this being shipped).
+   *
+   * Don't use this unless you need to read data written by previous versions of
+   * blink::ScriptValueSerializer.
+   */
+  void SetSupportsLegacyWireFormat(bool supports_legacy_wire_format);
+
+  /*
+   * Reads the underlying wire format version. Likely mostly to be useful to
+   * legacy code reading old wire format versions. Must be called after
+   * ReadHeader.
+   */
+  uint32_t GetWireFormatVersion() const;
+
+ private:
+  ValueDeserializer(const ValueDeserializer&) = delete;
+  void operator=(const ValueDeserializer&) = delete;
+
+  struct PrivateData;
+  PrivateData* private_;
+};
 
 /**
  * A map whose keys are referenced weakly. It is similar to JavaScript WeakMap