Install the local JVM resource before unpacking.

Fixes #78.

src/main/java/com/threerings/getdown/data/Resource.java

@@ -246,6 +246,17 @@ public class Resource
         }
     }
 
+    /**
+     * Installs the {@code getLocalNew} version of this resource to {@code getLocal}.
+     */
+    public void install () throws IOException {
+        File source = getLocalNew(), dest = getLocal();
+        log.info("- " + source);
+        if (!FileUtil.renameTo(source, dest)) {
+            throw new IOException("Failed to rename " + source + " to " + dest);
+        }
+    }
+
     /**
      * Unpacks this resource file into the directory that contains it. Returns
      * false if an error occurs while unpacking it.

src/main/java/com/threerings/getdown/launcher/Getdown.java

@@ -144,11 +144,7 @@ public abstract class Getdown extends Thread
         if (_readyToInstall) {
             log.info("Installing downloaded resources:");
             for (Resource resource : _toBeInstalledResouces) {
-                File source = resource.getLocalNew(), dest = resource.getLocal();
-                log.info("- " + source);
-                if (!FileUtil.renameTo(source, dest)) {
-                    throw new IOException("Failed to rename " + source + " to " + dest);
-                }
+                resource.install();
                 if (Thread.interrupted()) {
                     throw new InterruptedException("m.applet_stopped");
                 }
@@ -642,6 +638,7 @@ public abstract class Getdown extends Thread
         reportTrackingEvent("jvm_unpack", -1);
 
         updateStatus("m.unpacking_java");
+        vmjar.install();
         if (!vmjar.unpack()) {
             throw new IOException("m.java_unpack_failed");
         }