Add good example to documentation

java/ql/src/Security/CWE/CWE-200/AndroidWebViewSettingsPermitsContentAccess.qhelp

@@ -24,6 +24,9 @@
 
     <sample src="ContentAccessEnabled.java"/>
 
+    <p>In the following (good) example, access to <code>content://</code> URLs is explicitly denied.</p>
+
+    <sample src="ContentAccessDisabled.java"/>
   </example>
 
   <references>

java/ql/src/Security/CWE/CWE-200/ContentAccessDisabled.java

@@ -0,0 +1,3 @@
+WebSettings settings = webview.getSettings();
+
+settings.setAllowContentAccess(false);