[ios] Declare missing i variable in plugin_placeholder.js.

ios/web/web_state/js/resources/plugin_placeholder.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file adheres to closure-compiler conventions in order to enable
 // compilation with ADVANCED_OPTIMIZATIONS. See http://goo.gl/FwOgy
 //
 // Installs and runs the plugin placeholder function on the |__gCrWeb| object.
 
 /**
@@ skipping 110 matching lines @@
            (pluginHeight > windowHeight * significantFraction &&
             pluginWidth > minSize);
   };
 
   /**
    * Walks the list of detected plugin elements, adding a placeholder to any
    * that are "significant" (see above).
    * @param {string} message The message to show in the placeholder.
    */
   __gCrWeb['plugin']['addPluginPlaceholders'] = function(message) {
-    var plugins = __gCrWeb['placeholderTargetPlugins'];
+    var i, plugins = __gCrWeb['placeholderTargetPlugins'];
     for (i = 0; i < plugins.length; i++) {
       var plugin = plugins[i];
       if (!__gCrWeb['plugin'].isSignificantPlugin_(plugin)) {
         continue;
       }
 
       var pluginSize = __gCrWeb['plugin'].getPluginSize_(plugin);
       var widthStyle = pluginSize.width + 'px';
       var heightStyle = pluginSize.height + 'px';
 
@@ skipping 48 matching lines @@
       label.style.marginTop = imageSize + 'px';
       // Center horizontally.
       label.style.textAlign = 'center';
       label.textContent = message;
       placeholderBox.appendChild(label);
 
       plugin.insertBefore(placeholder, plugin.firstChild);
     }
   };
 }());  // End of anonymous object