Support external startup data in V8.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index c895c88b3cb213c686f6f9f0aadf2d13d3608374..b1da55e2c5ee0d2cf566c976b95dde2e0396a27b 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -4657,6 +4657,24 @@ class V8_EXPORT V8 {
   static void SetDecompressedStartupData(StartupData* decompressed_data);
 
   /**
+   * Hand startup data to V8, in case the embedder has chosen to build
+   * V8 with external startup data.
+   *
+   * Note:
+   * - By default the startup data is linked into the V8 library, in which
+   *   case this function is not meaningful.
+   * - If this needs to be called, it needs to be called before V8
+   *   tries to make use of its built-ins.
+   * - To avoid unnecessary copies of data, V8 will point directly into the
+   *   given data blob, so pretty please keep it around until V8 exit.
+   * - Compression of the startup blob might be useful, but needs to
+   *   handled entirely on the embedders' side.
+   * - The call will abort if the data is invalid.
+   */
+  static void SetNativesDataBlob(StartupData* startup_blob);
+  static void SetSnapshotDataBlob(StartupData* startup_blob);
+
+  /**
    * Adds a message listener.
    *
    * The same message listener can be added more than once and in that