Add a test to make sure source port cannot be transferred.

android_webview/java/src/org/chromium/android_webview/MessagePort.java

Index: android_webview/java/src/org/chromium/android_webview/MessagePort.java
diff --git a/android_webview/java/src/org/chromium/android_webview/MessagePort.java b/android_webview/java/src/org/chromium/android_webview/MessagePort.java
index e04035553a03630ff80d886558c469fc9101b7b1..4025c4507264c56d4fd753c4bd53be8e57955ece 100644
--- a/android_webview/java/src/org/chromium/android_webview/MessagePort.java
+++ b/android_webview/java/src/org/chromium/android_webview/MessagePort.java
@@ -70,7 +70,11 @@ public class MessagePort {
         if (msgPorts != null) {
             portIds = new int[msgPorts.length];
             for (int i = 0; i < msgPorts.length; i++) {
-                portIds[i] = msgPorts[i].portId();
+                int sentId = msgPorts[i].portId();
+                if (sentId == mPortId) {
+                    throw new IllegalStateException("Source port cannot be transferred");
+                }
+                portIds[i] = sentId;
             }
         }
         mMessagePortService.postMessage(mPortId, message, portIds);