Add a content API to create a message channel.

content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index cf404ccede7786d7b841e99bbf716a4cc07ae6d7..25169c86dfc2449adb00e636fb54c9019f765ce9 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -45,6 +45,7 @@ import android.view.accessibility.AccessibilityNodeProvider;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
 import android.view.inputmethod.InputMethodManager;
+import android.webkit.ValueCallback;
 import android.widget.FrameLayout;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -1396,6 +1397,16 @@ public class ContentViewCore
     }
 
     /**
+     * Creates a message channel.
+     *
+     * @param callback The message channel created or null if some error occurred.
+     */
+    public void createMessageChannel(ValueCallback<MessageChannel> callback) {
+        if (mNativeContentViewCore == 0) return;
+        nativeCreateMessageChannel(mNativeContentViewCore, callback);
+    }
+
+    /**
      * To be called when the ContentView is shown.
      */
     public void onShow() {
@@ -2558,6 +2569,12 @@ public class ContentViewCore
         attachImeAdapter();
     }
 
+    @CalledByNative
+    private static void onMessageChannelCreated(int portId1, int portId2,
+            ValueCallback<MessageChannel> callback) {
+        callback.onReceiveValue(new MessageChannel(portId1, portId2));
+    }
+
     /**
      * Attaches the native ImeAdapter object to the java ImeAdapter to allow communication via JNI.
      */
@@ -3303,6 +3320,9 @@ public class ContentViewCore
     private native void nativeEvaluateJavaScript(long nativeContentViewCoreImpl,
             String script, JavaScriptCallback callback, boolean startRenderer);
 
+    private native void nativeCreateMessageChannel(long nativeContentViewCoreImpl,
+            ValueCallback<MessageChannel> callback);
+
     private native long nativeGetNativeImeAdapter(long nativeContentViewCoreImpl);
 
     private native int nativeGetCurrentRenderProcessId(long nativeContentViewCoreImpl);