[piexwasm] Remove files app ImageOrientation dependency

JEITA EXIF image orientation is a number in [1..8]. PIEX C++ defaults
to 1 if there is no image orientation or its value is invalid. Return
the value in the PiexLoaderResponse and let the client code deal with
converting it to other types [1].

[1] In files app, make image_request_task.js convert the value in the
PiexLoaderResponse to ImageOrientation type. No change in behavior.

Bug: 1132695
Change-Id: I728680d17c31426d72b6b09bd52ee821540cbcd0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2432231Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Auto-Submit: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811119}

ui/file_manager/image_loader/image_request_task.js

@@ -334,7 +334,8 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
     this.piexLoader_.load(this.request_.url, chrome.runtime.reload)
         .then(
             function(data) {
-              this.request_.orientation = data.orientation;
+              this.request_.orientation =
+                  ImageOrientation.fromExifOrientation(data.orientation);
               this.request_.colorSpace = data.colorSpace;
               this.ifd_ = data.ifd;
               this.contentType_ = data.mimeType;

ui/file_manager/image_loader/piex_loader.js

@@ -89,11 +89,11 @@ function PiexLoaderResponse(data) {
   this.mimeType = data.mimeType || 'image/jpeg';
 
   /**
-   * @public {!ImageOrientation}
+   * JEITA EXIF image orientation being an integer in [1..8].
+   * @public {number}
    * @const
    */
-  this.orientation =
-      ImageOrientation.fromExifOrientation(data.orientation);
+  this.orientation = data.orientation;
 
   /**
    * @public {ColorSpace}