Enable posting a message from JS to Android webview.

android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java

Index: android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java b/android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java
index 77ad0ba9714cdad11a7085aa1cc0d2145e78ba12..36463ed622cde85810b4a857b7607eb46c7ead71 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java
@@ -28,6 +28,7 @@ public class AwBrowserContext {
     private AwFormDatabase mFormDatabase;
     private HttpAuthDatabase mHttpAuthDatabase;
     private DefaultAndroidKeyStore mLocalKeyStore;
+    private AwMessagePortService mMessagePortService;
 
     public AwBrowserContext(SharedPreferences sharedPreferences) {
         mSharedPreferences = sharedPreferences;
@@ -68,6 +69,13 @@ public class AwBrowserContext {
         return mLocalKeyStore;
     }
 
+    public AwMessagePortService createMessagePortService() {
+        if (mMessagePortService == null) {
+            mMessagePortService = new AwMessagePortService();
+        }
+        return mMessagePortService;
+    }
+
     /**
      * @see android.webkit.WebView#pauseTimers()
      */