[snapshot] support multiple contexts in the same snapshot.

src/bootstrapper.h

 // Copyright 2014 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_BOOTSTRAPPER_H_
 #define V8_BOOTSTRAPPER_H_
 
 #include "src/factory.h"
 
 namespace v8 {
@@ skipping 61 matching lines @@
 
   // Requires: Heap::SetUp has been called.
   void Initialize(bool create_heap_objects);
   void TearDown();
 
   // Creates a JavaScript Global Context with initial object graph.
   // The returned value is a global handle casted to V8Environment*.
   Handle<Context> CreateEnvironment(
       MaybeHandle<JSGlobalProxy> maybe_global_proxy,
       v8::Local<v8::ObjectTemplate> global_object_template,
-      v8::ExtensionConfiguration* extensions,
+      v8::ExtensionConfiguration* extensions, size_t context_snapshot_index,
       GlobalContextType context_type = FULL_CONTEXT);
 
   // Detach the environment from its outer global object.
   void DetachGlobal(Handle<Context> env);
 
   // Traverses the pointers for memory management.
   void Iterate(ObjectVisitor* v);
 
   // Accessor for the native scripts source code.
   template <class Source>
@@ skipping 77 matching lines @@
 
  private:
   const char* data_;
   size_t length_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_BOOTSTRAPPER_H_