This lets you set a custom user agent.

CustomUserAgent.java

package com.carnivalmobile.webviewhack;

import android.app.Activity;
import android.app.Application;
import android.os.Bundle;
import android.webkit.WebView;

import com.carnival.sdk.MessageActivity;

public class UserAgentHack implements Application.ActivityLifecycleCallbacks {

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

    }

    @Override
    public void onActivityStarted(Activity activity) {

    }

    @Override
    public void onActivityResumed(Activity activity) {
        if (activity instanceof MessageActivity) {
            WebView webView = (WebView) activity.findViewById(R.id.webView);
            if (webView != null) {
                webView.getSettings().setUserAgentString("Custom User Agent");
            }
        }
    }

    @Override
    public void onActivityPaused(Activity activity) {

    }

    @Override
    public void onActivityStopped(Activity activity) {

    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

    }

    @Override
    public void onActivityDestroyed(Activity activity) {

    }
}

// Call like this
registerActivityLifecycleCallbacks(new UserAgentHack());