[piexwasm] Make PiexLoader a namespace

PiexLoader has no |this| properties at all: it's a namespace with one
API called load() effectively, so no need to instance it with new. Do
the simpler thing: make it a namespace [1]. No change in behavior.

[1] See CL:2437316 review comments for the namespace discussion.

Bug: 1132695
Change-Id: I10319ede41bbaeb0caa0c8bab6ff4b7701ff3081
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437319Reviewed-by: Alex Danilo <adanilo@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812489}

ui/file_manager/image_loader/image_request_task.js

@@ -332,8 +332,7 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
 
   // Load RAW image source thumbnail.
   if (fileType.type === 'raw') {
-    const piexLoader = ImageRequestTask.getPiexLoaderInstance();
-    piexLoader.load(this.request_.url, chrome.runtime.reload)
+    PiexLoader.load(this.request_.url, chrome.runtime.reload)
         .then(
             function(data) {
               this.request_.orientation =
@@ -630,14 +629,3 @@ ImageRequestTask.prototype.cleanup_ = function() {
   this.canvas_.width = 0;
   this.canvas_.height = 0;
 };
-
-/**
- * Returns the singleton instance of the PiexLoader RAW image loader.
- * @return {!PiexLoader} PiexLoader object.
- */
-ImageRequestTask.getPiexLoaderInstance = function() {
-  if (!ImageRequestTask.piexLoaderInstance_) {
-    ImageRequestTask.piexLoaderInstance_ = new PiexLoader();
-  }
-  return ImageRequestTask.piexLoaderInstance_;
-};

ui/file_manager/image_loader/piex_loader.js

@@ -492,10 +492,9 @@ class ImageBuffer {
 }
 
 /**
- * Creates a PiexLoader.
- * @constructor
+ * PiexLoader: is a namespace.
  */
-function PiexLoader() {}
+const PiexLoader = {};
 
 /**
  * Loads a RAW image. Returns the image metadata and the image thumbnail in a
@@ -510,7 +509,7 @@ function PiexLoader() {}
  * @param {function()} onPiexModuleFailed
  * @return {!Promise<!PiexLoaderResponse>}
  */
-PiexLoader.prototype.load = function(source, onPiexModuleFailed) {
+PiexLoader.load = function(source, onPiexModuleFailed) {
   /** @type {?ImageBuffer} */
   let imageBuffer;