Lay groudwork to Closure compile JavaScript

ui/webui/resources/js/load_time_data.js

Index: ui/webui/resources/js/load_time_data.js
diff --git a/ui/webui/resources/js/load_time_data.js b/ui/webui/resources/js/load_time_data.js
index ee3d497d654cbc1d6729f96f83d5426039896992..a7efcdbb3ed52f6e7cc8333ce43e95cf2fbcc2fe 100644
--- a/ui/webui/resources/js/load_time_data.js
+++ b/ui/webui/resources/js/load_time_data.js
@@ -15,6 +15,7 @@ var loadTimeData;
 (function() {
   'use strict';
 
+  /** @constructor */
   function LoadTimeData() {
   }
 
@@ -29,6 +30,7 @@ var loadTimeData;
     },
 
     /**
+     * @param {string} id An ID of a value that might exist.
      * @return {boolean} True if |id| is a key in the dictionary.
      */
     valueExists: function(id) {
@@ -55,20 +57,21 @@ var loadTimeData;
     getString: function(id) {
       var value = this.getValue(id);
       expectIsType(id, value, 'string');
-      return value;
+      return /** @type {string} */ (value);
     },
 
     /**
      * Returns a formatted localized string where $1 to $9 are replaced by the
      * second to the tenth argument.
      * @param {string} id The ID of the string we want.
-     * @param {...string} The extra values to include in the formatted output.
+     * @param {...string} var_args The extra values to include in the formatted
+     *     output.
      * @return {string} The formatted string.
      */
-    getStringF: function(id) {
+    getStringF: function(id, var_args) {
       var value = this.getString(id);
       if (!value)
-        return;
+        return '';
 
       var varArgs = arguments;
       return value.replace(/\$[$1-9]/g, function(m) {
@@ -84,7 +87,7 @@ var loadTimeData;
     getBoolean: function(id) {
       var value = this.getValue(id);
       expectIsType(id, value, 'boolean');
-      return value;
+      return /** @type {boolean} */ (value);
     },
 
     /**
@@ -96,7 +99,7 @@ var loadTimeData;
       var value = this.getValue(id);
       expectIsType(id, value, 'number');
       expect(value == Math.floor(value), 'Number isn\'t integer: ' + value);
-      return value;
+      return /** @type {number} */ (value);
     },
 
     /**