[filesapp] Address TODO: use renderOrientation_ for RAW images

Use the this.renderOrientation_ feature for better cache keying of RAW
image thumbnails from piexwasm. The client's this.request_.orientation
forms part of the image loader cache key: we should leave it alone and
using this.renderOrientation_ allows us to do that.

To be clear, further testing of RAW images that have EXIF orientation,
has shown that they are _not_ affected by issue 1152084.

Bug: 1152084
Change-Id: I7665985df51ddecdb4bb5bebf2437f910d82330b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2569317
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Auto-Submit: Noel Gordon <noel@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833051}

ui/file_manager/image_loader/image_request_task.js

@@ -396,8 +396,7 @@ ImageRequestTask.prototype.downloadThumbnail_ = function(onSuccess, onFailure) {
     PiexLoader.load(this.request_.url, chrome.runtime.reload)
         .then(
             function(data) {
-              // TODO(crbug.com/1152084): use this.renderOrientation_.
-              this.request_.orientation =
+              this.renderOrientation_ =
                   ImageOrientation.fromExifOrientation(data.orientation);
               this.ifd_ = data.ifd;
               this.contentType_ = data.mimeType;