Add a content API to create a message channel.

content/public/browser/message_port_provider.h

Index: content/public/browser/message_port_provider.h
diff --git a/content/public/browser/message_port_provider.h b/content/public/browser/message_port_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..2c91c36511c639a80a4dbf8b7368c0ed81ae55fe
--- /dev/null
+++ b/content/public/browser/message_port_provider.h
@@ -0,0 +1,39 @@
+// Copyright (c) 2014 The Chromium 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 CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
+#define CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class WebContents;
+
+// An interface consisting of methods that can be called to use Message ports.
+class CONTENT_EXPORT MessagePortProvider {
+ public:
+  // Should be called on IO Thread.
+  static void PostMessageToFrame(WebContents* web_contents,

[jochen (gone - plz use gerrit), 2014/11/18 13:29:41]

please document what these methods do and how you're supposed to call them

[sgurun-gerrit only, 2014/11/18 22:51:55]

Done.

+                                 base::string16* source_origin,

[jochen (gone - plz use gerrit), 2014/11/18 13:29:41]

why aren't these const refs?

[sgurun-gerrit only, 2014/11/18 22:51:55]

Done.

+                                 base::string16* target_origin,
+                                 base::string16* data,
+                                 std::vector<int>* ports);
+  // Should be called on IO Thread.
+  static void CreateMessageChannel(WebContents* web_contents,
+                                   int* port1,
+                                   int* port2);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(MessagePortProvider);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_