App list: TileItemView::SetAppListItem exits early if item already set.

This effectively caches the result of CalculateKMeanColorOfBitmap so it
does not have to be recomputed every time the start page view is reset.
Noticeable improvement in the time it takes to switch to the start page.

BUG=382795

Review URL: https://codereview.chromium.org/326023002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@277407 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 10 insertions, 0 deletions

diff --git a/ui/app_list/views/tile_item_view.cc b/ui/app_list/views/tile_item_view.cc
index c73f9e0..f587a0c 100644
--- a/ui/app_list/views/tile_item_view.cc
+++ b/ui/app_list/views/tile_item_view.cc
@@ -94,6 +94,10 @@ TileItemView::TileItemView()
   title_->SetFontList(rb.GetFontList(kItemTextFontStyle));
   title_->SetHorizontalAlignment(gfx::ALIGN_CENTER);
 
+  // When |item_| is NULL, the tile is invisible. Calling SetAppListItem with a
+  // non-NULL item makes the tile visible.
+  SetVisible(false);
+
   AddChildView(icon_);
   AddChildView(title_);
 }
@@ -102,6 +106,12 @@ TileItemView::~TileItemView() {
 }
 
 void TileItemView::SetAppListItem(AppListItem* item) {
+  // TODO(calamity): This will not update if the contents of |item_| have
+  // changed since it was last assigned. Add an observer to refresh when the
+  // item changes.
+  if (item == item_)
+    return;
+
   item_ = item;
   if (!item) {
     SetVisible(false);