Fix cookie logic for webviews

Clear cookies before webview is started and load the webview in the
async response after cookie clearing is complete.
Remove unnecessary webview and cookie cleanup code.
Set the default webview client to prevent system browser redirects

Test: manual verify hyperlink does not open in system browser
Test: manual verify through IODT testing
Bug: 282129516
Change-Id: Ifee0d702440e89aa07196fefa810d85a64899493

packages/CarrierDefaultApp/assets/slice_purchase_test.html

@@ -81,5 +81,7 @@
         Dismiss flow
     </button>
     <p id="dismiss_flow"></p>
+
+    <h2>Test <a href="http://www.google.com">hyperlink</a></h2>
 </body>
 </html>

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

@@ -29,6 +29,7 @@ import android.util.Log;
 import android.view.KeyEvent;
 import android.webkit.CookieManager;
 import android.webkit.WebView;
+import android.webkit.WebViewClient;
 
 import com.android.phone.slice.SlicePurchaseController;
 
@@ -113,8 +114,10 @@ public class SlicePurchaseActivity extends Activity {
             return;
         }
 
-        // Create and configure WebView
-        setupWebView();
+        // Clear any cookies that might be persisted from previous sessions before loading WebView
+        CookieManager.getInstance().removeAllCookies(value -> {
+            setupWebView();
+        });
     }
 
     protected void onPurchaseSuccessful() {
@@ -176,12 +179,7 @@ public class SlicePurchaseActivity extends Activity {
     private void setupWebView() {
         // 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();
+        mWebView.setWebViewClient(new WebViewClient());
 
         // Enable JavaScript for the carrier purchase website to send results back to
         //  the slice purchase application.