Enable posting a message from JS to Android webview.

android_webview/browser/aw_message_port_message_filter.h

Index: android_webview/browser/aw_message_port_message_filter.h
diff --git a/android_webview/browser/aw_message_port_message_filter.h b/android_webview/browser/aw_message_port_message_filter.h
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index 0000000000000000000000000000000000000000..98e609307f1b9e4453f0a42051bed1bb9db53c88
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+++ b/android_webview/browser/aw_message_port_message_filter.h
@@ -0,0 +1,45 @@
+// Copyright 2015 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 ANDROID_WEBVIEW_BROWSER_MESSAGE_PORT_MESSAGE_FILTER_H_
+#define ANDROID_WEBVIEW_BROWSER_MESSAGE_PORT_MESSAGE_FILTER_H_
+
+#include "base/callback.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/message_port_delegate.h"
+
+namespace android_webview {
+
+// Filter for Aw specific MessagePort related IPC messages (creating and
+// destroying a MessagePort, sending a message via a MessagePort etc).
+class AwMessagePortMessageFilter : public content::BrowserMessageFilter,
+                                   public content::MessagePortDelegate {
+ public:
+  explicit AwMessagePortMessageFilter(int routing_id);

[mnaganov (inactive), 2015/01/13 10:37:50]

nit: route_id

[sgurun-gerrit only, 2015/01/14 23:53:13]

Done.

+
+  // BrowserMessageFilter implementation.
+  void OnChannelClosing() override;
+  bool OnMessageReceived(const IPC::Message& message) override;
+  void OnDestruct() const override;
+
+  // MessagePortDelegate implementation.
+  void SendMessage(int msg_port_route_id,
+                   const base::string16& message,
+                   const std::vector<int>& sent_message_port_ids) override;
+  void SendMessagesAreQueued(int route_id) override;

[mnaganov (inactive), 2015/01/13 10:37:50]

The name is misleading. Sounds like as if the function returns a boolean, but it
is not. Should it be 'SendQueuedMessages'?

[sgurun-gerrit only, 2015/01/14 23:53:13]

Yes, quite confusing. It originates from MessagePortMessageFilter

void MessagePortMessageFilter::SendMessagesAreQueued(int route_id) {
  Send(new MessagePortMsg_MessagesQueued(route_id));
}

I think the name Send is to emphasize that it is sending an IPC:

// Tells the Message Port Channel object that there are no more in-flight
// messages arriving.
IPC_MESSAGE_ROUTED0(MessagePortMsg_MessagesQueued)

the IPC tells the port implementation at the renderer that the messages will
start to be queued at the browser side.
I think in the delegate we can easily drop the name Send, and call it
MessagesAreQueued. I am also open to any other name. I will put a TODO here to
address it when I start working on queuing messages.

[mnaganov (inactive), 2015/01/15 09:49:33]

Ah, sorry -- I actually missed somehow the fact that this method is inherited :)

+
+ private:
+  friend class content::BrowserThread;
+  friend class base::DeleteHelper<AwMessagePortMessageFilter>;
+
+  ~AwMessagePortMessageFilter() override;
+
+  int route_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(AwMessagePortMessageFilter);
+};
+
+}   // namespace android_webview
+
+#endif  // ANDROID_WEBVIEW_BROWSER_MESSAGE_PORT_MESSAGE_FILTER_H_