Return created channels synchronously

android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java

Index: android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java b/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
index b4aae2db27657dad9f8b40e85235cfbaea3aee84..a717a52939c8fc1f8e8081034d88702d94f47843 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
@@ -8,10 +8,11 @@ import android.os.Handler;
 import android.os.Looper;
 import android.os.Message;
 import android.util.SparseArray;
-import android.webkit.ValueCallback;
 
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
+import org.chromium.base.ObserverList;
+import org.chromium.base.ThreadUtils;
 
 /**
  * Provides the Message Channel functionality for Android Webview. Specifically
@@ -40,12 +41,18 @@ public class AwMessagePortService {
 
     private static final int POST_MESSAGE = 1;
 
-    // TODO(sgurun) implement transferring ports from JS to Java using message channels.
-    private static class PostMessage {
+    /**
+     * Observer for MessageChannel events.

[hush (inactive), 2015/02/13 03:25:08]

Do you plan to support observing more events other than creation?

[sgurun-gerrit only, 2015/02/13 05:11:59]

not at this time.

+     */
+    public static interface MessageChannelObserver {
+        void onMessageChannelCreated();
+    }
+
+    private static class PostMessageFromWeb {
         public MessagePort port;
         public String message;
 
-        public PostMessage(MessagePort port, String message) {
+        public PostMessageFromWeb(MessagePort port, String message) {
             this.port = port;
             this.message = message;
         }
@@ -59,7 +66,7 @@ public class AwMessagePortService {
             @Override
             public void handleMessage(Message msg) {
                 if (msg.what == POST_MESSAGE) {
-                    PostMessage m = (PostMessage) msg.obj;
+                    PostMessageFromWeb m = (PostMessageFromWeb) msg.obj;
                     m.port.onMessage(m.message);
                     return;
                 }
@@ -100,12 +107,22 @@ public class AwMessagePortService {
     private long mNativeMessagePortService;
     private MessagePortStorage mPortStorage = new MessagePortStorage();
     private MessageHandlerThread mMessageHandlerThread = new MessageHandlerThread();
+    private ObserverList<MessageChannelObserver> mObserverList =
+            new ObserverList<MessageChannelObserver>();
 
     AwMessagePortService() {
         mNativeMessagePortService = nativeInitAwMessagePortService();
         mMessageHandlerThread.start();
     }
 
+    public void addObserver(MessageChannelObserver observer) {
+        mObserverList.addObserver(observer);
+    }
+
+    public void removeObserver(MessageChannelObserver observer) {
+        mObserverList.removeObserver(observer);
+    }
+
     public void postMessage(int senderId, String message, int[] sentPorts) {
         // verify that webview still owns the port (not transferred)
         if (mPortStorage.get(senderId) == null) {
@@ -124,33 +141,44 @@ public class AwMessagePortService {
                 if (p == null) {
                     throw new IllegalStateException("Cannot transfer unknown port " + port);
                 }
-                p.close();

[hush (inactive), 2015/02/13 03:25:08]

why is this removed?

[sgurun-gerrit only, 2015/02/13 05:11:59]

I will implement the close() functionality in the next CL. Basically, I am
thinking we may not even need to close it here, because it is already in
transferred state, and any data structure allocated will be released here (and
in messageportservice) during transfer, but leaving to next CL for real.

-                // close the port so users can get feedback if they use in future.
                 mPortStorage.put(port, null);
             }
         }
     }
 
-    private MessagePort addPort(int portId) {
+    public MessagePort[] createMessageChannel() {
+        return new MessagePort[]{new MessagePort(this), new MessagePort(this)};
+    }
+
+    private MessagePort addPort(MessagePort m, int portId) {
         if (mPortStorage.get(portId) != null) {
             throw new IllegalStateException("Port already exists");
         }
-        MessagePort m = new MessagePort(portId, this);
+        m.setPortId(portId);
         mPortStorage.put(portId, m);
         return m;
     }
 
     @CalledByNative
     private void onMessageChannelCreated(int portId1, int portId2,
-            ValueCallback<MessagePort[]> callback) {
-        callback.onReceiveValue(new MessagePort[]{addPort(portId1), addPort(portId2)});
+            MessagePort[] ports) {
+        ThreadUtils.assertOnUiThread();
+        addPort(ports[0], portId1);
+        addPort(ports[1], portId2);
+        for (MessageChannelObserver observer : mObserverList) {
+            observer.onMessageChannelCreated();
+        }
     }
 
-    // Called on IO thread.
     @CalledByNative
     private void onPostMessage(int portId, String message, int[] ports) {
-        PostMessage m = new PostMessage(mPortStorage.get(portId), message);
+        ThreadUtils.assertOnUiThread();
+        PostMessageFromWeb m = new PostMessageFromWeb(mPortStorage.get(portId), message);
         Handler handler = mMessageHandlerThread.getHandler();
+        if (handler == null) {
+            // TODO(sgurun) handler could be null. But this logic will be removed.
+            return;
+        }
         Message msg = handler.obtainMessage(POST_MESSAGE, m);
         handler.sendMessage(msg);
     }