Fix how folder image item is drawn in folder icon

Fixes sizing when drawing image rep for the target scale - instead of
using the rep's pixel size, use DIP size multiplied by scale (in case
the icon image does not have exact representation for the target scale).

BUG=1018038

Change-Id: Idd184ffa34675816dc7b9a6b9d52eafc6c55c485
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888654Reviewed-by: Nic Hollingum <hollingum@google.com>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710865}

ash/app_list/model/folder_image.cc

@@ -104,8 +104,8 @@ void FolderImageSource::DrawIcon(gfx::Canvas* canvas,
 
   canvas->DrawImageIntInPixel(
       shadowed_rep, x * scale + shadow_margin.left(),
-      y * scale + shadow_margin.top(), shadowed_rep.pixel_width(),
-      shadowed_rep.pixel_height(), true, cc::PaintFlags());
+      y * scale + shadow_margin.top(), scale * shadowed.width(),
+      scale * shadowed.height(), true, cc::PaintFlags());
 }
 
 void FolderImageSource::Draw(gfx::Canvas* canvas) {