[snapshot] encode resource before serializing.

src/snapshot/natives.h

Index: src/snapshot/natives.h
diff --git a/src/snapshot/natives.h b/src/snapshot/natives.h
index 0f09e207dc4db5f1fe3591f15fb734d2c00fd469..79f7db39227bfd7fc309155b19623eacbdf6c074 100644
--- a/src/snapshot/natives.h
+++ b/src/snapshot/natives.h
@@ -5,6 +5,7 @@
 #ifndef V8_SNAPSHOT_NATIVES_H_
 #define V8_SNAPSHOT_NATIVES_H_
 
+#include "include/v8.h"
 #include "src/objects.h"
 #include "src/vector.h"
 
@@ -46,10 +47,6 @@ class V8_EXPORT_PRIVATE NativesCollection {
   static Vector<const char> GetScriptSource(int index);
   static Vector<const char> GetScriptName(int index);
   static Vector<const char> GetScriptsSource();
-
-  // The following methods are implemented in natives-common.cc:
-
-  static FixedArray* GetSourceCache(Heap* heap);
 };
 
 typedef NativesCollection<CORE> Natives;
@@ -64,6 +61,37 @@ void ReadNatives();
 void DisposeNatives();
 #endif
 
+class NativesExternalStringResource final
+    : public v8::String::ExternalOneByteStringResource {
+ public:
+  NativesExternalStringResource(NativeType type, int index);
+
+  const char* data() const override { return data_; }
+  size_t length() const override { return length_; }
+
+  v8::String::ExternalOneByteStringResource* EncodeForSerialization() const {
+    DCHECK(type_ == CORE || type_ == EXTRAS);
+    intptr_t val = (index_ << 1) | ((type_ == CORE) ? 0 : 1);
+    val = val << kPointerSizeLog2;  // Pointer align.
+    return reinterpret_cast<v8::String::ExternalOneByteStringResource*>(val);
+  }
+
+  // Decode from serialization.
+  static NativesExternalStringResource* DecodeForDeserialization(
+      const v8::String::ExternalOneByteStringResource* encoded) {
+    intptr_t val = reinterpret_cast<intptr_t>(encoded) >> kPointerSizeLog2;
+    NativeType type = (val & 1) ? EXTRAS : CORE;
+    int index = static_cast<int>(val >> 1);
+    return new NativesExternalStringResource(type, index);
+  }
+
+ private:
+  const char* data_;
+  size_t length_;
+  NativeType type_;
+  int index_;
+};
+
 }  // namespace internal
 }  // namespace v8