[fsp] Add support for providing thumbnails.

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');
 var fileSystemNatives = requireNative('file_system_natives');
 var GetDOMError = fileSystemNatives.GetDOMError;
 
 /**
+ * Maximum size of the thumbnail in bytes.
+ * @type {number}
+ * @const
+ */
+var METADATA_THUMBNAIL_SIZE_LIMIT = 32 * 1024 * 1024;
+
+/**
  * Annotates a date with its serialized value.
  * @param {Date} date Input date.
  * @return {Date} Date with an extra <code>value</code> attribute.
  */
 function annotateDate(date) {
   // Copy in case the input date is frozen.
   var result = new Date(date.getTime());
   result.value = result.toString();
   return result;
 }
 
 /**
+ * Verifies if the passed image URI is valid.
+ * @param {*} uri Image URI.
+ * @return {boolean} True if valid, valse otherwise.
+ */
+function verifyImageURI(uri) {
+  // The URI is specified by a user, so the type may be incorrect.
+  if (typeof uri != 'string' && !(uri instanceof String))
+    return false;
+
+  var uriLowerCase = uri.toLowerCase();

[hirono, 2014/08/29 03:58:32]

uri.substr(0, 20).toLowerCase() may be good for performance.

[mtomasz, 2014/08/29 05:20:26]

Good point. I optimized it in C++, but forgot about JS. Done.

+  return uriLowerCase.indexOf('data:image/png;') == 0 ||
+         uriLowerCase.indexOf('data:image/jpeg;') == 0 ||
+         uriLowerCase.indexOf('data:image/webp;') == 0;
+}
+
+/**
  * 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)
     result.mimeType = metadata.mimeType;
+  if ('thumbnail' in metadata)
+    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.
  */
 function massageArgumentsDefault(args, dispatch) {
@@ skipping 83 matching lines @@
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onUnmountRequested',
     massageArgumentsDefault);
 
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onGetMetadataRequested',
     function(args, dispatch) {
       var executionStart = Date.now();
       var options = args[0];
       var onSuccessCallback = function(metadata) {
+        // 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) {
+          fileSystemProviderInternal.operationRequestedError(
+              options.fileSystemId, options.requestId, 'FAILED',
+              Date.now() - executionStart);
+          throw new 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))
+          throw new Error('Thumbnail format invalid.');
+        if ('thumbnail' in metadata &&
+            metadata.thumbnail.length > METADATA_THUMBNAIL_SIZE_LIMIT) {
+          throw new Error('Thumbnail data too large.');
+        }
+
         fileSystemProviderInternal.getMetadataRequestedSuccess(
             options.fileSystemId,
             options.requestId,
             annotateMetadata(metadata),
             Date.now() - executionStart);
       };
       var onErrorCallback = function(error) {
         fileSystemProviderInternal.operationRequestedError(
             options.fileSystemId, options.requestId, error,
             Date.now() - executionStart);
       }
       dispatch([options, onSuccessCallback, onErrorCallback]);
     });
 
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onReadDirectoryRequested',
     function(args, dispatch) {
       var executionStart = Date.now();
       var options = args[0];
       var onSuccessCallback = function(entries, hasNext) {
         var annotatedEntries = entries.map(annotateMetadata);
+        // It is invalid to return a thumbnail when it's not requested.
+        annotatedEntries.forEach(function(metadata) {
+          if (metadata.thumbnail) {
+            fileSystemProviderInternal.operationRequestedError(
+                options.fileSystemId, options.requestId, 'FAILED',
+                Date.now() - executionStart);
+            throw new Error(
+                'Thumbnails must not be provided when reading a directory.');
+          }
+        });
         fileSystemProviderInternal.readDirectoryRequestedSuccess(
             options.fileSystemId, options.requestId, annotatedEntries, hasNext,
             Date.now() - executionStart);
       };
       var onErrorCallback = function(error) {
         fileSystemProviderInternal.operationRequestedError(
             options.fileSystemId, options.requestId, error,
             Date.now() - executionStart);
       }
       dispatch([options, onSuccessCallback, onErrorCallback]);
@@ skipping 51 matching lines @@
 
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onWriteFileRequested',
     massageArgumentsDefault);
 
 eventBindings.registerArgumentMassager(
     'fileSystemProvider.onAbortRequested',
     massageArgumentsDefault);
 
 exports.binding = binding.generate();