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

public/platform/WebMessagePortChannelClient.h

Index: public/platform/WebMessagePortChannelClient.h
diff --git a/public/platform/WebMessagePortChannelClient.h b/public/platform/WebMessagePortChannelClient.h
index 9389338bc37d6c01d478ca50332773e55574cf69..aafd6e7b1d73550f96d670078ce780b31b197435 100644
--- a/public/platform/WebMessagePortChannelClient.h
+++ b/public/platform/WebMessagePortChannelClient.h
@@ -31,10 +31,13 @@
 #ifndef WebMessagePortChannelClient_h
 #define WebMessagePortChannelClient_h
 
+#include <v8.h>
+
 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
@@ -42,6 +45,20 @@ public:
     // 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 a V8 context messages sent to this port can be (de)serialized in.
+    // Can return null if no valid V8 context could be determined.
+    // 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.
+    // FIXME: Remove this method when no longer needed (http://crbug.com/461906)
+    virtual v8::Local<v8::Context> scriptContextForMessageConversion() = 0;
+
 protected:
     ~WebMessagePortChannelClient() { }
 };