Eliminate all UI thread decoding of extension images....

chrome/browser/cocoa/location_bar_view_mac.mm

Index: chrome/browser/cocoa/location_bar_view_mac.mm
===================================================================
--- chrome/browser/cocoa/location_bar_view_mac.mm	(revision 42362)
+++ chrome/browser/cocoa/location_bar_view_mac.mm	(working copy)
@@ -630,12 +630,11 @@
   if (!page_action_->default_icon_path().empty())
     icon_paths.push_back(page_action_->default_icon_path());
 
-  tracker_ = new ImageLoadingTracker(this, icon_paths.size());
   for (std::vector<std::string>::iterator iter = icon_paths.begin();
        iter != icon_paths.end(); ++iter) {
-    tracker_->PostLoadImageTask(extension->GetResource(*iter),
-                                gfx::Size(Extension::kPageActionIconMaxSize,
-                                          Extension::kPageActionIconMaxSize));
+    tracker_.PostLoadImageTask(extension->GetResource(*iter),
+                               gfx::Size(Extension::kPageActionIconMaxSize,
+                                         Extension::kPageActionIconMaxSize));
   }
 
   registrar_.Add(this, NotificationType::EXTENSION_HOST_VIEW_SHOULD_CLOSE,
@@ -643,8 +642,6 @@
 }
 
 LocationBarViewMac::PageActionImageView::~PageActionImageView() {
-  if (tracker_)
-    tracker_->StopTrackingImageLoad();
 }
 
 NSSize LocationBarViewMac::PageActionImageView::GetPreferredImageSize() {
@@ -689,28 +686,24 @@
   }
 }
 
-void LocationBarViewMac::PageActionImageView::OnImageLoaded(SkBitmap* image,
-                                                            size_t index) {
+void LocationBarViewMac::PageActionImageView::OnImageLoaded(
+    SkBitmap* image, int index) {
   // We loaded icons()->size() icons, plus one extra if the Page Action had
   // a default icon.
-  int total_icons = page_action_->icon_paths()->size();
+  int total_icons = static_cast<int>(page_action_->icon_paths()->size());
   if (!page_action_->default_icon_path().empty())
     total_icons++;
-  DCHECK(static_cast<int>(index) < total_icons);
+  DCHECK(index < total_icons);
 
   // Map the index of the loaded image back to its name. If we ever get an
   // index greater than the number of icons, it must be the default icon.
   if (image) {
-    if (index < page_action_->icon_paths()->size())
+    if (index < total_icons)
       page_action_icons_[page_action_->icon_paths()->at(index)] = *image;
     else
       page_action_icons_[page_action_->default_icon_path()] = *image;
   }
 
-  // If we are done, release the tracker.
-  if (static_cast<int>(index) == (total_icons - 1))
-    tracker_ = NULL;
-
   owner_->UpdatePageActions();
 
   if (preview_enabled_)