Bug 597304. Change wording for manual cache size override. r=gavin a=beta7

browser/components/preferences/advanced.js

@@ -191,8 +191,7 @@ var gAdvancedPane = {
    *
    * browser.cache.disk.capacity
    * - the size of the browser cache in KB
-   * browser.cache.disk.smart_size.enabled
-   * - If disabled, disk.capacity is used
+   * - Only used if browser.cache.disk.smart_size.enabled is disabled
    */
 
   /**
@@ -243,8 +242,10 @@ var gAdvancedPane = {
 
   readSmartSizeEnabled: function ()
   {
-    var enabled = document.getElementById("browser.cache.disk.smart_size.enabled").value;
-    this.updateCacheSizeUI(enabled);
+    // The smart_size.enabled preference element is inverted="true", so its
+    // value is the opposite of the actual pref value
+    var disabled = document.getElementById("browser.cache.disk.smart_size.enabled").value;
+    this.updateCacheSizeUI(!disabled);
   },
   
   /**