Fix the issue that the padding at the right edge is missing

|icons_size| should contain the padding space on both edges. This CL
fixes such an issue.


Bug: 1009483
Change-Id: Ibfd44f5e70bd345fe9b623aa4ff2377ddb4c8250
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832463
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701374}

ash/shelf/scrollable_shelf_view.cc

@@ -765,7 +765,8 @@ gfx::Insets ScrollableShelfView::CalculateEdgePadding() const {
     return CalculatePaddingForDisplayCentering();
 
   const int icons_size = shelf_view_->GetSizeOfAppIcons(
-      shelf_view_->number_of_visible_apps(), false);
+                             shelf_view_->number_of_visible_apps(), false) +
+                         2 * GetAppIconEndPadding();
   const int base_padding = ShelfConfig::Get()->app_icon_group_margin();
 
   const int available_size_for_app_icons =
@@ -795,7 +796,8 @@ gfx::Insets ScrollableShelfView::CalculateEdgePadding() const {
 
 gfx::Insets ScrollableShelfView::CalculatePaddingForDisplayCentering() const {
   const int icons_size = shelf_view_->GetSizeOfAppIcons(
-      shelf_view_->number_of_visible_apps(), false);
+                             shelf_view_->number_of_visible_apps(), false) +
+                         2 * GetAppIconEndPadding();
   const gfx::Rect display_bounds =
       screen_util::GetDisplayBoundsWithShelf(GetWidget()->GetNativeWindow());
   const int display_size_primary = GetShelf()->PrimaryAxisValue(