Require that the "wifi.enabled" flag in appengine-web.xml be set to

true to enable WiFi use of MIT App Inventor. As of this commit, this
is shipped set to false.

Change-Id: Ib053a3d8173a7684c4748525b138a20cd6d62395

appinventor/appengine/src/com/google/appinventor/server/project/utils/JavaWebStart.java

@@ -7,6 +7,7 @@ package com.google.appinventor.server.project.utils;
 
 import com.google.appinventor.common.version.GitBuildId;
 import com.google.appinventor.server.encryption.EncryptionException;
+import com.google.appinventor.server.flags.Flag;
 import com.google.appinventor.shared.rpc.ServerLayout;
 import com.google.appinventor.shared.rpc.user.UserInfoProvider;
 
@@ -40,6 +41,8 @@ public final class JavaWebStart {
 
   private static final String VERSION_PREFIX_DELIMITER = "_";
 
+  private static final Flag<Boolean> wifiEnabled = Flag.createFlag("wifi.enabled", false);
+
   private JavaWebStart() {  // COV_NF_LINE
   }  // COV_NF_LINE
 
@@ -141,6 +144,10 @@ public final class JavaWebStart {
     for (String jarFile : jarFiles) {
       jnlp.append("      <jar href=\"").append(jarFile).append("\"/>\n");
     }
+
+    if (wifiEnabled.get())
+      jnlp.append("      <property name=\"wifi.enabled\" value=\"true\"/>\n");
+
     jnlp.append("   </resources>\n")
         .append("   <application-desc main-class=\"").append(mainClass).append("\">\n");
     for (String arg : args) {

appinventor/appengine/war/WEB-INF/appengine-web.xml

@@ -51,6 +51,12 @@
          buildserver to match -->
     <property name="build.send.git.version" value="true" />
 
+    <!-- Set this to true to enable the use of Wifi connections from the blocks editor to
+         the phone. The phone must have an up-to-date copy of the MIT AICompanion App to
+         use this feature. -->
+
+    <property name="wifi.enabled" value="false" />
+
   </system-properties>
 
   <!-- Enable concurrency in the app engine server -->

appinventor/blockslib/src/openblocks/codeblockutil/CDeviceSelector.java

@@ -90,8 +90,13 @@ public class CDeviceSelector extends JMenuBar {
     } else {
       connectedIcon = new ImageIcon(descriptor);
     }
+
+    if (System.getProperty("wifi.enabled") != null && System.getProperty("wifi.enabled").equals("true")) {
       addDevice("WiFi");          // Add the WiFi device, so now there will always be at least one
-                                // which means that the noDevicesPlaceholder can be deprecated
+                                  // which means that the noDevicesPlaceholder can be deprecated when WiFi is enabled.
+    } else {
+      System.out.println("Wifi Disabled");
+    }
   }
 
   public void addCallback(DeviceSelectedCallback callback) {