wm: Fix icon misplaced after zooming in and out.

Removes a unnecessary SetSize call after updating the icon. It is
unnecessary because we should be using the bounds specified by Layout.

Test: manual
Bug: 1069428
Change-Id: Ia3c24ed4c94472236c193f1fc85569af36d8e647
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145952Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758339}

ash/wm/window_mini_view.cc

@@ -168,7 +168,6 @@ void WindowMiniView::UpdateIconView() {
   }
 
   icon_view_->SetImage(ModifyIcon(icon));
-  icon_view_->SetSize(kIconSize);
 }
 
 gfx::Rect WindowMiniView::GetContentAreaBounds() const {