Add a class to replace ImageLoadingTracker with a nicer API.

chrome/browser/extensions/extension_system.cc

Index: chrome/browser/extensions/extension_system.cc
diff --git a/chrome/browser/extensions/extension_system.cc b/chrome/browser/extensions/extension_system.cc
index cf5b5d451641efe65d414bd09684c4c30aefa38b..cfafc07b8067efeca273b1e7a435c016cc64abf4 100644
--- a/chrome/browser/extensions/extension_system.cc
+++ b/chrome/browser/extensions/extension_system.cc
@@ -24,6 +24,7 @@
 #include "chrome/browser/extensions/extension_process_manager.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
+#include "chrome/browser/extensions/image_loader.h"
 #include "chrome/browser/extensions/lazy_background_task_queue.h"
 #include "chrome/browser/extensions/management_policy.h"
 #include "chrome/browser/extensions/navigation_observer.h"
@@ -240,6 +241,12 @@ EventRouter* ExtensionSystemImpl::Shared::event_router() {
   return extension_event_router_.get();
 }
 
+ImageLoader* ExtensionSystemImpl::Shared::image_loader() {
+  if (!image_loader_)
+    image_loader_.reset(new ImageLoader());
+  return image_loader_.get();
+}
+
 //
 // ExtensionSystemImpl
 //
@@ -360,6 +367,10 @@ RulesRegistryService* ExtensionSystemImpl::rules_registry_service() {
   return rules_registry_service_.get();
 }
 
+ImageLoader* ExtensionSystemImpl::image_loader() {
+  return shared_->image_loader();
+}
+
 ApiResourceManager<SerialConnection>*
 ExtensionSystemImpl::serial_connection_manager() {
   return serial_connection_manager_.get();