Clear cookies and webview state for new purchase requests

Cookie store is separate from WebView and persisted to the device, so it
could be saved across sessions. Clear any state that might be saved for
each new request.

Test: manual verify during IODT
Bug: 282129516
Change-Id: If97c57dd1c49e1c6971ff99c6b8aa0834f62ee00

packages/CarrierDefaultApp/src/com/android/carrierdefaultapp/SlicePurchaseActivity.java

@@ -27,6 +27,7 @@ import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.KeyEvent;
+import android.webkit.CookieManager;
 import android.webkit.WebView;
 
 import com.android.phone.slice.SlicePurchaseController;
@@ -168,6 +169,12 @@ public class SlicePurchaseActivity extends Activity {
         // Create WebView
         mWebView = new WebView(this);
 
+        // Clear any cookies and state that might be saved from previous sessions
+        CookieManager.getInstance().removeAllCookies(null);
+        CookieManager.getInstance().flush();
+        mWebView.clearCache(true);
+        mWebView.clearHistory();
+
         // Enable JavaScript for the carrier purchase website to send results back to
         //  the slice purchase application.
         mWebView.getSettings().setJavaScriptEnabled(true);