Fix the ARC icon scale mismatch issue.

When the ARC raw icon image rep has the correct size, it should be
added to the imageskia as well, otherwise, the imageskia might miss the
rep for one scale, which could cause the scale mismatching issue.

BUG=1124679

Change-Id: Ib6332a0b0924afff590a72b3c4e3158522f254c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2472718Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Nancy Wang <nancylingwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817303}

chrome/browser/apps/app_service/app_icon_factory.cc

@@ -158,6 +158,7 @@ gfx::ImageSkia ExtractSubsetForArcImage(const gfx::ImageSkia& image_skia) {
   gfx::ImageSkia subset_image;
   for (const auto& rep : image_skia.image_reps()) {
     if (IsConsistentPixelSize(rep, image_skia)) {
+      subset_image.AddRepresentation(rep);
       continue;
     }