Use const/let in image loader.

ImageLoader still has many vars in its scripts.
It will make presubmit linter unhappy even when we modify an line in
a file in the future.
Let me eliminate all vars beforehand.

Bug: 778674
Test: Confirm that thumbnails of image files (incl. raw files) are correct.
Change-Id: I6960d6c37f9791f4d3ad52be0cbf607af3bd8337
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1991056
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729645}

ui/file_manager/image_loader/cache.js

@@ -54,8 +54,8 @@ ImageCache.prototype.initialize = function(callback) {
   // Establish a connection to the database or (re)create it if not available
   // or not up to date. After changing the database's schema, increment
   // ImageCache.DB_VERSION to force database recreating.
-  var openRequest = window.indexedDB.open(
-      ImageCache.DB_NAME, ImageCache.DB_VERSION);
+  const openRequest =
+      window.indexedDB.open(ImageCache.DB_NAME, ImageCache.DB_VERSION);
 
   openRequest.onsuccess = function(e) {
     this.db_ = e.target.result;
@@ -66,7 +66,7 @@ ImageCache.prototype.initialize = function(callback) {
 
   openRequest.onupgradeneeded = function(e) {
     console.info('Cache database creating or upgrading.');
-    var db = e.target.result;
+    const db = e.target.result;
     if (db.objectStoreNames.contains('metadata')) {
       db.deleteObjectStore('metadata');
     }
@@ -91,9 +91,9 @@ ImageCache.prototype.initialize = function(callback) {
  * @private
  */
 ImageCache.prototype.setCacheSize_ = function(size, opt_transaction) {
-  var transaction = opt_transaction ||
-      this.db_.transaction(['settings'], 'readwrite');
-  var settingsStore = transaction.objectStore('settings');
+  const transaction =
+      opt_transaction || this.db_.transaction(['settings'], 'readwrite');
+  const settingsStore = transaction.objectStore('settings');
 
   settingsStore.put({key: 'size', value: size});  // Update asynchronously.
 };
@@ -109,10 +109,10 @@ ImageCache.prototype.setCacheSize_ = function(size, opt_transaction) {
  */
 ImageCache.prototype.fetchCacheSize_ = function(
     onSuccess, onFailure, opt_transaction) {
-  var transaction = opt_transaction ||
+  const transaction = opt_transaction ||
       this.db_.transaction(['settings', 'metadata', 'data'], 'readwrite');
-  var settingsStore = transaction.objectStore('settings');
-  var sizeRequest = settingsStore.get('size');
+  const settingsStore = transaction.objectStore('settings');
+  const sizeRequest = settingsStore.get('size');
 
   sizeRequest.onsuccess = function(e) {
     if (e.target.result) {
@@ -141,7 +141,7 @@ ImageCache.prototype.fetchCacheSize_ = function(
  */
 ImageCache.prototype.evictCache_ = function(
     size, onSuccess, onFailure, opt_transaction) {
-  var transaction = opt_transaction ||
+  const transaction = opt_transaction ||
       this.db_.transaction(['settings', 'metadata', 'data'], 'readwrite');
 
   // Check if the requested size is smaller than the cache size.
@@ -150,7 +150,7 @@ ImageCache.prototype.evictCache_ = function(
     return;
   }
 
-  var onCacheSize = function(cacheSize) {
+  const onCacheSize = function(cacheSize) {
     if (size < ImageCache.MEMORY_LIMIT - cacheSize) {
       // Enough space, no need to evict.
       this.setCacheSize_(cacheSize + size, transaction);
@@ -158,21 +158,21 @@ ImageCache.prototype.evictCache_ = function(
       return;
     }
 
-    var bytesToEvict = Math.max(size, ImageCache.EVICTION_CHUNK_SIZE);
+    let bytesToEvict = Math.max(size, ImageCache.EVICTION_CHUNK_SIZE);
 
     // Fetch all metadata.
-    var metadataEntries = [];
-    var metadataStore = transaction.objectStore('metadata');
-    var dataStore = transaction.objectStore('data');
+    const metadataEntries = [];
+    const metadataStore = transaction.objectStore('metadata');
+    const dataStore = transaction.objectStore('data');
 
-    var onEntriesFetched = function() {
+    const onEntriesFetched = function() {
       metadataEntries.sort(function(a, b) {
         return b.lastLoadTimestamp - a.lastLoadTimestamp;
       });
 
-      var totalEvicted = 0;
+      let totalEvicted = 0;
       while (bytesToEvict > 0) {
-        var entry = metadataEntries.pop();
+        const entry = metadataEntries.pop();
         totalEvicted += entry.size;
         bytesToEvict -= entry.size;
         metadataStore.delete(entry.key);  // Remove asynchronously.
@@ -183,7 +183,7 @@ ImageCache.prototype.evictCache_ = function(
     }.bind(this);
 
     metadataStore.openCursor().onsuccess = function(e) {
-      var cursor = e.target.result;
+      const cursor = e.target.result;
       if (cursor) {
         metadataEntries.push(cursor.value);
         cursor.continue();
@@ -214,8 +214,8 @@ ImageCache.prototype.saveImage = function(
     return;
   }
 
-  var onNotFoundInCache = function() {
-    var metadataEntry = {
+  const onNotFoundInCache = function() {
+    const metadataEntry = {
       key: key,
       timestamp: timestamp,
       width: width,
@@ -225,14 +225,14 @@ ImageCache.prototype.saveImage = function(
       lastLoadTimestamp: Date.now(),
     };
 
-    var dataEntry = {key: key, data: data};
+    const dataEntry = {key: key, data: data};
 
-    var transaction = this.db_.transaction(['settings', 'metadata', 'data'],
-                                           'readwrite');
-    var metadataStore = transaction.objectStore('metadata');
-    var dataStore = transaction.objectStore('data');
+    const transaction =
+        this.db_.transaction(['settings', 'metadata', 'data'], 'readwrite');
+    const metadataStore = transaction.objectStore('metadata');
+    const dataStore = transaction.objectStore('data');
 
-    var onCacheEvicted = function() {
+    const onCacheEvicted = function() {
       metadataStore.put(metadataEntry);  // Add asynchronously.
       dataStore.put(dataEntry);  // Add asynchronously.
     };
@@ -263,19 +263,19 @@ ImageCache.prototype.loadImage = function(
     return;
   }
 
-  var transaction = this.db_.transaction(['settings', 'metadata', 'data'],
-                                         'readwrite');
-  var metadataStore = transaction.objectStore('metadata');
-  var dataStore = transaction.objectStore('data');
-  var metadataRequest = metadataStore.get(key);
-  var dataRequest = dataStore.get(key);
+  const transaction =
+      this.db_.transaction(['settings', 'metadata', 'data'], 'readwrite');
+  const metadataStore = transaction.objectStore('metadata');
+  const dataStore = transaction.objectStore('data');
+  const metadataRequest = metadataStore.get(key);
+  const dataRequest = dataStore.get(key);
 
-  var metadataEntry = null;
-  var metadataReceived = false;
-  var dataEntry = null;
-  var dataReceived = false;
+  let metadataEntry = null;
+  let metadataReceived = false;
+  let dataEntry = null;
+  let dataReceived = false;
 
-  var onPartialSuccess = function() {
+  const onPartialSuccess = function() {
     // Check if all sub-requests have finished.
     if (!metadataReceived || !dataReceived) {
       return;
@@ -352,17 +352,17 @@ ImageCache.prototype.removeImage = function(
     return;
   }
 
-  var transaction = opt_transaction ||
+  const transaction = opt_transaction ||
       this.db_.transaction(['settings', 'metadata', 'data'], 'readwrite');
-  var metadataStore = transaction.objectStore('metadata');
-  var dataStore = transaction.objectStore('data');
+  const metadataStore = transaction.objectStore('metadata');
+  const dataStore = transaction.objectStore('data');
 
-  var cacheSize = null;
-  var cacheSizeReceived = false;
-  var metadataEntry = null;
-  var metadataReceived = false;
+  let cacheSize = null;
+  let cacheSizeReceived = false;
+  let metadataEntry = null;
+  let metadataReceived = false;
 
-  var onPartialSuccess = function() {
+  const onPartialSuccess = function() {
     if (!cacheSizeReceived || !metadataReceived) {
       return;
     }
@@ -385,11 +385,11 @@ ImageCache.prototype.removeImage = function(
     dataStore.delete(key);  // Delete asynchronously.
   }.bind(this);
 
-  var onCacheSizeFailure = function() {
+  const onCacheSizeFailure = function() {
     cacheSizeReceived = true;
   };
 
-  var onCacheSizeSuccess = function(result) {
+  const onCacheSizeSuccess = function(result) {
     cacheSize = result;
     cacheSizeReceived = true;
     onPartialSuccess();
@@ -399,7 +399,7 @@ ImageCache.prototype.removeImage = function(
   this.fetchCacheSize_(onCacheSizeSuccess, onCacheSizeFailure, transaction);
 
   // Receive image's metadata.
-  var metadataRequest = metadataStore.get(key);
+  const metadataRequest = metadataStore.get(key);
 
   metadataRequest.onsuccess = function(e) {
     if (e.target.result) {

ui/file_manager/image_loader/cache_unittest.js

@@ -5,7 +5,7 @@
 'use strict';
 
 function testCreateCacheKey() {
-  let key = LoadImageRequest.cacheKey({url: 'http://example.com/image.jpg'});
+  const key = LoadImageRequest.cacheKey({url: 'http://example.com/image.jpg'});
   assertTrue(!!key);
 }
 

ui/file_manager/image_loader/image_loader.js

@@ -38,8 +38,8 @@ function ImageLoader() {
                 {volumeId: event.volumeMetadata.volumeId}, function() {});
           }
         });
-    var initPromises = volumeMetadataList.map(function(volumeMetadata) {
-      var requestPromise = new Promise(function(callback) {
+    const initPromises = volumeMetadataList.map(function(volumeMetadata) {
+      const requestPromise = new Promise(function(callback) {
         chrome.fileSystem.requestFileSystem(
             {volumeId: volumeMetadata.volumeId},
             /** @type {function(FileSystem=)} */(callback));
@@ -87,11 +87,11 @@ ImageLoader.prototype.onIncomingRequest_ = function(
     return;
   }
 
-  var request = /** @type {!LoadImageRequest} */ (request_data);
+  const request = /** @type {!LoadImageRequest} */ (request_data);
 
   // Sending a response may fail if the receiver already went offline.
   // This is not an error, but a normal and quite common situation.
-  let failSafeSendResponse = function(response) {
+  const failSafeSendResponse = function(response) {
     try {
       sendResponse(response);
     } catch (e) {
@@ -124,14 +124,14 @@ ImageLoader.prototype.onIncomingRequest_ = function(
  * @private
  */
 ImageLoader.prototype.onMessage_ = function(senderId, request, callback) {
-  var requestId = senderId + ':' + request.taskId;
+  const requestId = senderId + ':' + request.taskId;
   if (request.cancel) {
     // Cancel a task.
     this.scheduler_.remove(requestId);
     return false;  // No callback calls.
   } else {
     // Create a request task and add it to the scheduler (queue).
-    var requestTask = new ImageRequest(
+    const requestTask = new ImageRequest(
         requestId, this.cache_, this.piexLoader_, request, callback);
     this.scheduler_.add(requestTask);
     return true;  // Request will call the callback.

ui/file_manager/image_loader/image_loader_client.js

@@ -189,7 +189,7 @@ ImageLoaderClient.CACHE_MEMORY_LIMIT = 20 * 1024 * 1024;  // 20 MB.
  * @return {?number} Remote task id or null if loaded from cache.
  */
 ImageLoaderClient.loadToImage = function(request, image, onSuccess, onError) {
-  var callback = function(result) {
+  const callback = function(result) {
     if (result.status == LoadImageResponseStatus.ERROR) {
       onError();
       return;

ui/file_manager/image_loader/image_loader_client_unittest.js

@@ -40,7 +40,7 @@ function loadAndCheckCacheUsed(client, url, cache) {
     }
   };
 
-  let request = LoadImageRequest.createForUrl(url);
+  const request = LoadImageRequest.createForUrl(url);
   request.cache = cache;
 
   return new Promise(function(fulfill) {
@@ -51,7 +51,7 @@ function loadAndCheckCacheUsed(client, url, cache) {
 }
 
 function testCache(callback) {
-  var client = new ImageLoaderClient();
+  const client = new ImageLoaderClient();
   reportPromise(
       loadAndCheckCacheUsed(client, 'http://example.com/image.jpg', true)
           .then(function(cacheUsed) {
@@ -66,7 +66,7 @@ function testCache(callback) {
 }
 
 function testNoCache(callback) {
-  var client = new ImageLoaderClient();
+  const client = new ImageLoaderClient();
   reportPromise(
       loadAndCheckCacheUsed(client, 'http://example.com/image.jpg', false)
           .then(function(cacheUsed) {
@@ -81,7 +81,7 @@ function testNoCache(callback) {
 }
 
 function testDataURLCache(callback) {
-  var client = new ImageLoaderClient();
+  const client = new ImageLoaderClient();
   reportPromise(
       loadAndCheckCacheUsed(client, 'data:URI', true)
           .then(function(cacheUsed) {

ui/file_manager/image_loader/image_loader_unittest.js

@@ -20,15 +20,15 @@ function calculateCopyParametersFromOptions(source, options) {
  * - Target: max size is 100x100
  */
 function testNormalImage() {
-  var source = new Image();
+  const source = new Image();
   source.width = 200;
   source.height = 50;
-  var options = {
+  const options = {
     maxWidth: 100,
     maxHeight: 100,
     orientation: ImageOrientation.fromClockwiseRotation(0)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(0, result.source.x);
   assertEquals(0, result.source.y);
   assertEquals(200, result.source.width);
@@ -47,15 +47,15 @@ function testNormalImage() {
  * - Target: max size is 100x100
  */
 function testRotatedImage() {
-  var source = new Image();
+  const source = new Image();
   source.width = 50;
   source.height = 200;
-  var options = {
+  const options = {
     maxWidth: 100,
     maxHeight: 100,
     orientation: ImageOrientation.fromClockwiseRotation(1)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(0, result.source.x);
   assertEquals(0, result.source.y);
   assertEquals(50, result.source.width);
@@ -74,16 +74,16 @@ function testRotatedImage() {
  * - Target: 50x50 cropped image.
  */
 function testCroppedImage() {
-  var source = new Image();
+  const source = new Image();
   source.width = 800;
   source.height = 100;
-  var options = {
+  const options = {
     width: 50,
     height: 50,
     crop: true,
     orientation: ImageOrientation.fromClockwiseRotation(0)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(350, result.source.x);
   assertEquals(0, result.source.y);
   assertEquals(100, result.source.width);
@@ -102,16 +102,16 @@ function testCroppedImage() {
  * - Target: 50x50 cropped image.
  */
 function testCroppedImageWithResize() {
-  var source = new Image();
+  const source = new Image();
   source.width = 200;
   source.height = 25;
-  var options = {
+  const options = {
     width: 50,
     height: 50,
     crop: true,
     orientation: ImageOrientation.fromClockwiseRotation(0)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(87, result.source.x);
   assertEquals(0, result.source.y);
   assertEquals(25, result.source.width);
@@ -130,16 +130,16 @@ function testCroppedImageWithResize() {
  * - Target: 50x50 cropped image.
  */
 function testCroppedTinyImage() {
-  var source = new Image();
+  const source = new Image();
   source.width = 20;
   source.height = 10;
-  var options = {
+  const options = {
     width: 50,
     height: 50,
     crop: true,
     orientation: ImageOrientation.fromClockwiseRotation(0)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(5, result.source.x);
   assertEquals(0, result.source.y);
   assertEquals(10, result.source.width);
@@ -158,16 +158,16 @@ function testCroppedTinyImage() {
  * - Target: 50x50 cropped image
  */
 function testCroppedRotatedImage() {
-  var source = new Image();
+  const source = new Image();
   source.width = 100;
   source.height = 400;
-  var options = {
+  const options = {
     width: 50,
     height: 50,
     crop: true,
     orientation: ImageOrientation.fromClockwiseRotation(1)
   };
-  var result = calculateCopyParametersFromOptions(source, options);
+  const result = calculateCopyParametersFromOptions(source, options);
   assertEquals(0, result.source.x);
   assertEquals(150, result.source.y);
   assertEquals(100, result.source.width);

ui/file_manager/image_loader/image_loader_util.js

@@ -95,7 +95,7 @@ ImageLoaderUtil.resizeAndCrop = function(source, target, request) {
   target.height = copyParameters.canvas.height;
 
   // Apply.
-  let targetContext =
+  const targetContext =
       /** @type {CanvasRenderingContext2D} */ (target.getContext('2d'));
   targetContext.save();
   request.orientation.cancelImageOrientation(
@@ -208,10 +208,10 @@ ImageLoaderUtil.convertColorSpace = function(target, colorSpace) {
   }
   if (colorSpace === ColorSpace.ADOBE_RGB) {
     const matrix = ImageLoaderUtil.MATRIX_FROM_ADOBE_TO_STANDARD;
-    let context =
+    const context =
         assertInstanceof(target.getContext('2d'), CanvasRenderingContext2D);
-    let imageData = context.getImageData(0, 0, target.width, target.height);
-    let data = imageData.data;
+    const imageData = context.getImageData(0, 0, target.width, target.height);
+    const data = imageData.data;
     for (let i = 0; i < data.length; i += 4) {
       // Scale to [0, 1].
       let adobeR = data[i] / 255;

ui/file_manager/image_loader/piex/tests.js

@@ -47,7 +47,7 @@ const puppeteer = require('puppeteer');
     headless: !program.debug
   });
 
-  let page = await browser.newPage();
+  const page = await browser.newPage();
 
   await page.setViewport({
     width: 1200, height: 800

ui/file_manager/image_loader/piex_loader.js

@@ -16,13 +16,13 @@ console.log('[PiexLoader] wasm mode loaded');
  *   image: function(number, number):PiexWasmImageResult
  * }}
  */
-var PiexWasmModule;
+let PiexWasmModule;
 
 /**
  * |window| var Module defined in page <script src='piex/piex.js.wasm'>.
  * @type {PiexWasmModule}
  */
-var Module = window['Module'] || {};
+const PiexModule = window['Module'] || {};
 
 /**
  * Set true only if the wasm Module.onAbort() handler is called.
@@ -35,7 +35,7 @@ let wasmFailed = false;
  * the Module has failed and re-throws the error.
  * @throws {!Error|string}
  */
-Module.onAbort = (error) => {
+PiexModule.onAbort = (error) => {
   wasmFailed = true;
   throw error;
 };
@@ -49,7 +49,7 @@ Module.onAbort = (error) => {
  * broken Module state.
  */
 function wasmModuleFailed() {
-  if (wasmFailed || !Module.calledRun) {
+  if (wasmFailed || !PiexModule.calledRun) {
     console.error('[PiexLoader] wasmModuleFailed');
     setTimeout(chrome.runtime.reload, 0);
     return true;
@@ -178,7 +178,7 @@ function readFromFileSystem(url) {
  *  length:number
  * }}
  */
-var PiexWasmPreviewImageMetadata;
+let PiexWasmPreviewImageMetadata;
 
 /**
  * The piex wasm Module.image(<raw image source>,...) API returns |error|, or
@@ -196,7 +196,7 @@ var PiexWasmPreviewImageMetadata;
  *  details:?Object
  * }}
  */
-var PiexWasmImageResult;
+let PiexWasmImageResult;
 
 /**
  * Piex wasm raw image preview image extractor.
@@ -242,13 +242,13 @@ class ImageBuffer {
    * @throws {!Error}
    */
   process() {
-    this.memory = Module._malloc(this.length);
+    this.memory = PiexModule._malloc(this.length);
     if (!this.memory) {
       throw new Error('Image malloc failed: ' + this.length + ' bytes');
     }
 
-    Module.HEAP8.set(this.source, this.memory);
-    const result = Module.image(this.memory, this.length);
+    PiexModule.HEAP8.set(this.source, this.memory);
+    const result = PiexModule.image(this.memory, this.length);
     if (result.error) {
       throw new Error(result.error);
     }
@@ -310,7 +310,7 @@ class ImageBuffer {
       return null;
     }
 
-    let format = {};
+    const format = {};
     for (const [key, value] of Object.entries(details)) {
       if (typeof value === 'string') {
         format[key] = value.replace(/\0+$/, '').trim();
@@ -330,7 +330,7 @@ class ImageBuffer {
    * Release resources.
    */
   close() {
-    Module._free(this.memory);
+    PiexModule._free(this.memory);
   }
 }
 

ui/file_manager/image_loader/request.js

@@ -273,13 +273,13 @@ ImageRequest.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
   }.bind(this);
 
   // Download data urls directly since they are not supported by XmlHttpRequest.
-  var dataUrlMatches = this.request_.url.match(/^data:([^,;]*)[,;]/);
+  const dataUrlMatches = this.request_.url.match(/^data:([^,;]*)[,;]/);
   if (dataUrlMatches) {
     this.image_.src = this.request_.url;
     this.contentType_ = dataUrlMatches[1];
     return;
   }
-  var drivefsUrlMatches = this.request_.url.match(/^drivefs:(.*)/);
+  const drivefsUrlMatches = this.request_.url.match(/^drivefs:(.*)/);
   if (drivefsUrlMatches) {
     window.webkitResolveLocalFileSystemURL(
         drivefsUrlMatches[1],
@@ -300,21 +300,24 @@ ImageRequest.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
     return;
   }
 
-  var fileType = FileType.getTypeForName(this.request_.url);
+  const fileType = FileType.getTypeForName(this.request_.url);
 
   // Load RAW images by using Piex loader instead of XHR.
   if (fileType.type === 'raw') {
-    this.piexLoader_.load(this.request_.url).then(function(data) {
-      var blob = new Blob([data.thumbnail], {type: 'image/jpeg'});
-      var url = URL.createObjectURL(blob);
-      this.image_.src = url;
-      this.request_.orientation = data.orientation;
-      this.request_.colorSpace = data.colorSpace;
-      this.ifd_ = data.ifd;
-    }.bind(this), function() {
-      // The error has already been logged in PiexLoader.
-      onFailure();
-    });
+    this.piexLoader_.load(this.request_.url)
+        .then(
+            function(data) {
+              const blob = new Blob([data.thumbnail], {type: 'image/jpeg'});
+              const url = URL.createObjectURL(blob);
+              this.image_.src = url;
+              this.request_.orientation = data.orientation;
+              this.request_.colorSpace = data.colorSpace;
+              this.ifd_ = data.ifd;
+            }.bind(this),
+            function() {
+              // The error has already been logged in PiexLoader.
+              onFailure();
+            });
     return;
   }
 
@@ -330,7 +333,7 @@ ImageRequest.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
   }
 
   // Fetch the image via XHR and parse it.
-  var parseImage = function(contentType, blob) {
+  const parseImage = function(contentType, blob) {
     if (contentType) {
       this.contentType_ = contentType;
     }
@@ -396,8 +399,8 @@ ImageRequest.prototype.load = function(url, onSuccess, onFailure) {
   this.aborted_ = false;
 
   // Do not call any callbacks when aborting.
-  var onMaybeSuccess = /** @type {function(string, Blob)} */ (
-      function(contentType, response) {
+  const onMaybeSuccess =
+      /** @type {function(string, Blob)} */ (function(contentType, response) {
         // When content type is not available, try to estimate it from url.
         if (!contentType) {
           contentType =
@@ -409,7 +412,7 @@ ImageRequest.prototype.load = function(url, onSuccess, onFailure) {
         }
       }.bind(this));
 
-  var onMaybeFailure = /** @type {function(number=)} */ (function(opt_code) {
+  const onMaybeFailure = /** @type {function(number=)} */ (function(opt_code) {
     if (!this.aborted_) {
       onFailure();
     }
@@ -417,7 +420,7 @@ ImageRequest.prototype.load = function(url, onSuccess, onFailure) {
 
   // The query parameter is workaround for crbug.com/379678, which forces the
   // browser to obtain the latest contents of the image.
-  var noCacheUrl = url + '?nocache=' + Date.now();
+  const noCacheUrl = url + '?nocache=' + Date.now();
   this.xhr_ = ImageRequest.load_(noCacheUrl, onMaybeSuccess, onMaybeFailure);
 };
 
@@ -427,7 +430,7 @@ ImageRequest.prototype.load = function(url, onSuccess, onFailure) {
  * @return {string} Extracted extension, e.g. png.
  */
 ImageRequest.prototype.extractExtension_ = function(url) {
-  var result = (/\.([a-zA-Z]+)$/i).exec(url);
+  const result = (/\.([a-zA-Z]+)$/i).exec(url);
   return result ? result[1] : '';
 };
 
@@ -443,7 +446,7 @@ ImageRequest.prototype.extractExtension_ = function(url) {
  * @private
  */
 ImageRequest.load_ = function(url, onSuccess, onFailure) {
-  let xhr = new XMLHttpRequest();
+  const xhr = new XMLHttpRequest();
   xhr.responseType = 'blob';
 
   xhr.onreadystatechange = function() {
@@ -454,8 +457,8 @@ ImageRequest.load_ = function(url, onSuccess, onFailure) {
       onFailure(xhr.status);
       return;
     }
-    let response = /** @type {Blob} */ (xhr.response);
-    let contentType = xhr.getResponseHeader('Content-Type') || response.type;
+    const response = /** @type {Blob} */ (xhr.response);
+    const contentType = xhr.getResponseHeader('Content-Type') || response.type;
     onSuccess(contentType, response);
   }.bind(this);
 

ui/file_manager/image_loader/scheduler.js

@@ -82,17 +82,17 @@ Scheduler.prototype.add = function(request) {
  * @param {string} requestId Unique ID of the request.
  */
 Scheduler.prototype.remove = function(requestId) {
-  var request = this.requests_[requestId];
+  const request = this.requests_[requestId];
   if (!request) {
     return;
   }
 
   // Remove from the internal queues with pending tasks.
-  var newIndex = this.pendingRequests_.indexOf(request);
+  const newIndex = this.pendingRequests_.indexOf(request);
   if (newIndex != -1) {
     this.newRequests_.splice(newIndex, 1);
   }
-  var pendingIndex = this.pendingRequests_.indexOf(request);
+  const pendingIndex = this.pendingRequests_.indexOf(request);
   if (pendingIndex != -1) {
     this.pendingRequests_.splice(pendingIndex, 1);
   }
@@ -137,7 +137,7 @@ Scheduler.prototype.continue_ = function() {
   // Run only up to MAXIMUM_IN_PARALLEL in the same time.
   while (this.pendingRequests_.length &&
          this.activeRequests_.length < Scheduler.MAXIMUM_IN_PARALLEL) {
-    var request = this.pendingRequests_.shift();
+    const request = this.pendingRequests_.shift();
     this.activeRequests_.push(request);
 
     // Try to load from cache. If doesn't exist, then download.
@@ -157,7 +157,7 @@ Scheduler.prototype.continue_ = function() {
  * @private
  */
 Scheduler.prototype.finish_ = function(request) {
-  var index = this.activeRequests_.indexOf(request);
+  const index = this.activeRequests_.indexOf(request);
   if (index < 0) {
     console.warn('Request not found.');
   }