웹뷰에서 tel: sms: 가 안됩니다

package com.hybrid.sample;import android.content.Intent;import android.net.Uri;import android.os.Bundle;import android.os.Handler;import android.os.Process;import android.support.v7.app.AppCompatActivity;import android.view.KeyEvent;import android.view.View;import android.webkit.WebView;import android.webkit.WebViewClient;import android.widget.Toast;public class MainActivity extends AppCompatActivity {    private WebView mWebView;    private String mCurrentUrl;    private final static String MAIN_URL = "http://sir.kr";    // BACK 2번 클릭 시 종료 핸들러. 플래그    private Handler mHandler = new Handler();    private boolean mFlag = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //스플래시        startActivity(new Intent(this, SplashActivity.class));        //웹뷰 설정        mWebView = (WebView) findViewById(R.id.web);        mWebView.getSettings().setJavaScriptEnabled(true);        //mWebView.setInitialScale(100);        mWebView.setLayerType(View.LAYER_TYPE_HARDWARE, null);        mWebView.getSettings().setUseWideViewPort(true);        mWebView.getSettings().setLoadWithOverviewMode(true);        mWebView.setWebViewClient(new WebViewClientClass());        mWebView.loadUrl(MAIN_URL);    }    private class WebViewClientClass extends WebViewClient {        public boolean shouldOverrideUrlLoading(WebView view, String overrideUrl) {            view.loadUrl(overrideUrl);            return true;        }    }    @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK) {            if (mWebView.getOriginalUrl().equalsIgnoreCase(MAIN_URL)) {                if (!mFlag) {                    Toast.makeText(this, "뒤로 버튼을 한번 더 누르시면 종료됩니다.", Toast.LENGTH_SHORT).show();    // 종료안내 toast 를 출력                    mFlag = true;                    mHandler.sendEmptyMessageDelayed(0, 2000);    // 2000ms 만큼 딜레이                    return false;                } else {                    // 앱 종료 code                    moveTaskToBack(true);                    finish();                    android.os.Process.killProcess(Process.myPid());                }            } else {                // 뒤로 가기 실행                if (mWebView.canGoBack()) {                    mWebView.goBack();                    return true;                }            }        }        return true;    }    public boolean shouldOverrideUrlLoading(WebView view, String url) {        if( url.startsWith("http:") || url.startsWith("https:") ) {            return false;        }        // Otherwise allow the OS to handle it        else if (url.startsWith("tel:")) {            Intent tel = new Intent(Intent.ACTION_DIAL, Uri.parse(url));            startActivity(tel);            return true;        }        else if (url.startsWith("mailto:")) {            String body = "Enter your Question, Enquiry or Feedback below:\n\n";            Intent mail = new Intent(Intent.ACTION_SEND);            mail.setType("application/octet-stream");            mail.putExtra(Intent.EXTRA_EMAIL, new String[]{"email address"});            mail.putExtra(Intent.EXTRA_SUBJECT, "Subject");            mail.putExtra(Intent.EXTRA_TEXT, body);            startActivity(mail);            return true;        }        return true;    }}