Expose v8 context a MessagePort lives in to give content side code a valid context to (de)serialize…

public/platform/WebMessagePortChannelClient.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebMessagePortChannelClient_h
 #define WebMessagePortChannelClient_h
 
+namespace v8 {
+class Context;
+template<typename T> class Handle;
+class Isolate;
+}
+
 namespace blink {
 
 // Provides an interface for users of WebMessagePortChannel to be notified
-// when messages are available.
+// when messages are available. This also gives users of WebMessagePortChannel
+// access to the V8 Context this message port lives in.
 class WebMessagePortChannelClient {
 public:
     // Alerts that new messages have arrived, which are retrieved by calling
     // WebMessagePortChannel::tryGetMessage. Note that this may be called
     // on any thread.
     virtual void messageAvailable() = 0;
 
+    // Returns the V8 isolate this message port lives in.
+    // Do not rely on this API, it is only exposed so content code can convert
+    // messages to base::Value, and will be removed when this conversion can be
+    // integrated into blink itself.
+    virtual v8::Isolate* scriptIsolate() = 0;
+
+    // Returns the V8 context this message port lives in.

[haraken, 2015/02/24 10:35:33]

As jochen pointed out, using a wrong context is a security hazard.

Just help me understand: What V8 context do you want to return here? A message
port is not a thing associated with a V8 context, so "the V8 context this
message port lives in" doesn't make sense to me...

+    // Do not rely on this API, it is only exposed so content code can convert
+    // messages to base::Value, and will be removed when this conversion can be
+    // integrated into blink itself.
+    virtual v8::Handle<v8::Context> scriptContext() = 0;
+
 protected:
     ~WebMessagePortChannelClient() { }
 };
 
 } // namespace blink
 
 #endif