Make painting app list items more efficient by caching the labels.

ui/app_list/views/app_list_item_view.cc

Index: ui/app_list/views/app_list_item_view.cc
diff --git a/ui/app_list/views/app_list_item_view.cc b/ui/app_list/views/app_list_item_view.cc
index dcf023a2f3dcd7021afd92f47cae30f6dee3b2f7..640aa57f6cd1d8d98eee4f6814be1e47f1c04bbb 100644
--- a/ui/app_list/views/app_list_item_view.cc
+++ b/ui/app_list/views/app_list_item_view.cc
@@ -10,6 +10,7 @@
 #include "grit/ui_resources.h"
 #include "ui/app_list/app_list_item_model.h"
 #include "ui/app_list/views/apps_grid_view.h"
+#include "ui/app_list/views/cached_label.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/base/animation/throb_animation.h"
 #include "ui/base/resource/resource_bundle.h"
@@ -65,7 +66,7 @@ AppListItemView::AppListItemView(AppsGridView* apps_grid_view,
       model_(model),
       apps_grid_view_(apps_grid_view),
       icon_(new views::ImageView),
-      title_(new views::Label),
+      title_(new CachedLabel),
       ui_state_(UI_STATE_NORMAL),
       touch_dragging_(false) {
   icon_->set_interactive(false);
@@ -77,6 +78,7 @@ AppListItemView::AppListItemView(AppsGridView* apps_grid_view,
   title_->SetFont(rb.GetFont(ui::ResourceBundle::SmallBoldFont));
   title_->SetHorizontalAlignment(gfx::ALIGN_LEFT);
   title_->SetVisible(!model_->is_installing());
+  title_->Invalidate();

[benwells, 2013/03/12 04:58:11]

nit: is this needed? CachedLabel initializes needs_repaint_ to true.

[koz (OOO until 15th September), 2013/03/13 00:30:36]

Not needed, but needs_repaint_ could just as easily initialise to false. I also
think this adds clarity.

 
   const gfx::ShadowValue kIconShadows[] = {
     gfx::ShadowValue(gfx::Point(0, 2), 2, SkColorSetARGB(0x24, 0, 0, 0)),
@@ -176,6 +178,7 @@ void AppListItemView::ItemIconChanged() {
 
 void AppListItemView::ItemTitleChanged() {
   title_->SetText(UTF8ToUTF16(model_->title()));
+  title_->Invalidate();
 }
 
 void AppListItemView::ItemHighlightedChanged() {
@@ -296,6 +299,7 @@ void AppListItemView::StateChanged() {
     model_->SetHighlighted(false);
     title_->SetEnabledColor(kTitleColor);
   }
+  title_->Invalidate();
 }
 
 bool AppListItemView::ShouldEnterPushedState(const ui::Event& event) {