Do not call stat() when reading directories via File API.

chrome/renderer/resources/extensions/file_system_provider_custom_bindings.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.
 
 // Custom binding for the fileSystemProvider API.
 
 var binding = require('binding').Binding.create('fileSystemProvider');
 var fileSystemProviderInternal =
     require('binding').Binding.create('fileSystemProviderInternal').generate();
 var eventBindings = require('event_bindings');
@@ skipping 42 matching lines @@
 /**
  * Annotates an entry metadata by serializing its modifiedTime value.
  * @param {EntryMetadata} metadata Input metadata.
  * @return {EntryMetadata} metadata Annotated metadata, which can be passed
  *     back to the C++ layer.
  */
 function annotateMetadata(metadata) {
   var result = {
     isDirectory: metadata.isDirectory,
     name: metadata.name,
-    size: metadata.size,
-    modificationTime: annotateDate(metadata.modificationTime)
   };
-  if ('mimeType' in metadata)
+  if (metadata.size !== undefined)
+    result.size = metadata.size;
+  if (metadata.modificationTime !== undefined)
+    result.modificationTime = annotateDate(metadata.modificationTime);
+  if (metadata.mimeType !== undefined)
     result.mimeType = metadata.mimeType;
-  if ('thumbnail' in metadata)
+  if (metadata.thumbnail !== undefined)
     result.thumbnail = metadata.thumbnail;
   return result;
 }
 
 /**
  * Massages arguments of an event raised by the File System Provider API.
  * @param {Array<*>} args Input arguments.
  * @param {function(Array<*>)} dispatch Closure to be called with massaged
  *     arguments.
  */
@@ skipping 16 matching lines @@
     'fileSystemProvider.onUnmountRequested',
     massageArgumentsDefault);
 
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onGetMetadataRequested',
     function(args, dispatch) {
       var executionStart = Date.now();
       var options = args[0];
       var onSuccessCallback = function(metadata) {
         var error;
+        // TODO(mtomasz): Remove the following two fields once crbug.com/413161
+        // is landed.
+        if (options.size !== undefined)
+          error = 'Size is required for this event.';
+        if (options.modificationTime !== undefined)
+          error = 'Last modified time is required for this event.';
+
         // It is invalid to return a thumbnail when it's not requested. The
         // restriction is added in order to avoid fetching the thumbnail while
         // it's not needed.
         if (!options.thumbnail && metadata.thumbnail)
           error = 'Thumbnail data provided, but not requested.';
 
         // Check the format and size. Note, that in the C++ layer, there is
         // another sanity check to avoid passing any evil URL.
         if ('thumbnail' in metadata && !verifyImageURI(metadata.thumbnail))
           error = 'Thumbnail format invalid.';
@@ skipping 175 matching lines @@
       var onSuccessCallback = function() {
         // TODO(mtomasz): To be implemented.
       };
       var onErrorCallback = function(error) {
         // TODO(mtomasz): To be implemented.
       }
       dispatch([onSuccessCallback, onErrorCallback]);
     });
 
 exports.binding = binding.generate();