[piexwasm] Include the image size in the malloc() failure Error

Bug: 935285
Change-Id: Id2810b266440a339f5dbbe7fd9f3814f5e24ad23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616838Reviewed-by: Alex Danilo <adanilo@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661255}

ui/file_manager/image_loader/piex_loader.js

@@ -514,7 +514,7 @@ class ImageBuffer {
   process() {
     this.memory = Module._malloc(this.length);
     if (!this.memory) {
-      throw new Error('Image malloc failure');
+      throw new Error('Image malloc failed: ' + this.length + ' bytes');
     }
 
     Module.HEAP8.set(this.source, this.memory);