[snapshot] support multiple contexts in the same snapshot.

include/v8.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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 6774 matching lines @@
 
   ~SnapshotCreator();
 
   /**
    * \returns the isolate prepared by the snapshot creator.
    */
   Isolate* GetIsolate();
 
   /**
    * Add a context to be included in the snapshot blob.
+   * \returns the index of the context in the snapshot blob.
    */
-  void AddContext(Local<Context> context);
+  int AddContext(Local<Context> context);

[jochen (gone - plz use gerrit), 2016/06/13 15:24:19]

size_t?

[Yang, 2016/06/14 11:45:30]

This is supposed to mirror the argument of Context::New, and just an index. So I
thought int would be fine.

 
   /**
    * Created a snapshot data blob.
    * \param function_code_handling whether to include compiled function code
    *        in the snapshot.
    * \returns { nullptr, 0 } on failure, and a startup snapshot on success. The
    *        caller acquires ownership of the data array in the return value.
    */
   StartupData CreateBlob(FunctionCodeHandling function_code_handling);
 
@@ skipping 283 matching lines @@
    *
    * \param global_object An optional global object to be reused for
    * the newly created context. This global object must have been
    * created by a previous call to Context::New with the same global
    * template. The state of the global object will be completely reset
    * and only object identify will remain.
    */
   static Local<Context> New(
       Isolate* isolate, ExtensionConfiguration* extensions = NULL,
       Local<ObjectTemplate> global_template = Local<ObjectTemplate>(),
-      Local<Value> global_object = Local<Value>());
+      Local<Value> global_object = Local<Value>(),
+      int context_snapshot_index = 0);

[vogelheim, 2016/06/13 16:20:20]

The argument context_snapshot_index has no \param section in the function
comment.

Should default be 0, or some invalid value (-1 or whatnot) for a non-snapshot
context?

[Yang, 2016/06/14 11:45:30]

0 as default reflects the current behavior. To create a context from scratch
(non-snapshot), you would have to set the default snapshot to null.

 
   /**
    * Sets the security token for the context.  To access an object in
    * another context, the security tokens must match.
    */
   void SetSecurityToken(Local<Value> token);
 
   /** Restores the security token to the default value. */
   void UseDefaultSecurityToken();
 
@@ skipping 1745 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_