Fix a bug with shelf icon centering

This fixes an issue where the app list button position wasn't properly
calculated, causing the shelf icons to sometimes "bleed" over the app
list button.

Bug: 805612
Bug: 869649
Change-Id: Id774e15edbde8704789ed77bb36da194060fc3e9
Reviewed-on: https://chromium-review.googlesource.com/1173753Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583026}

ash/shelf/shelf_view.cc

@@ -989,8 +989,6 @@ void ShelfView::CalculateIdealBounds(gfx::Rect* overflow_bounds) const {
     // opacity 0 anyways.
     if (i == kBackButtonIndex && !IsTabletModeEnabled())
       continue;
-    if (i == kAppListButtonIndex)
-      app_list_button_position = shelf_->PrimaryAxisValue(x, y);
 
     // There is no spacing between the first two elements. Do not worry about y
     // since the back button only appears in tablet mode, which forces the shelf
@@ -998,6 +996,9 @@ void ShelfView::CalculateIdealBounds(gfx::Rect* overflow_bounds) const {
     x = shelf_->PrimaryAxisValue(x + w + (i == 0 ? 0 : button_spacing), x);
     y = shelf_->PrimaryAxisValue(y, y + h + button_spacing);
 
+    if (i == kAppListButtonIndex)
+      app_list_button_position = shelf_->PrimaryAxisValue(x, y);
+
     if (i == separator_index) {
       // Place the separator halfway between the two icons it separates,
       // vertically centered.