Fix the incorrect icon issue for Mac.

The function GetIconPurpose uses the parameter |size_hint_in_dip| to
calculate the max supported pixel size, however, the input parameter
|icon_size_in_px_| is incorrect, and |size_hint_in_dip_| should be used.

BUG=1121480

Change-Id: I249f369e194eca9db96d8d2da68a9bdac03dedcc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377667Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Nancy Wang <nancylingwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802090}

chrome/browser/apps/app_service/app_icon_factory.cc

@@ -543,7 +543,7 @@ void IconLoadingPipeline::LoadWebAppIcon(
   icon_scale_for_compressed_response_ = icon_scale_;
 
   base::Optional<IconPurpose> icon_purpose_to_read =
-      GetIconPurpose(web_app_id, icon_manager, icon_size_in_px_);
+      GetIconPurpose(web_app_id, icon_manager, size_hint_in_dip_);
 
   if (!icon_purpose_to_read.has_value()) {
     MaybeLoadFallbackOrCompleteEmpty();