Revert "Move ExtensionCache to //extensions"

chrome/browser/extensions/updater/extension_cache_impl.h

Index: chrome/browser/extensions/updater/extension_cache_impl.h
diff --git a/chrome/browser/extensions/updater/extension_cache_impl.h b/chrome/browser/extensions/updater/extension_cache_impl.h
index b541d5dfaf16c30f9cea808e39da9a3faff5a8b2..444d455ec3c20a8a206cbce064cbbc2022dc69fa 100644
--- a/chrome/browser/extensions/updater/extension_cache_impl.h
+++ b/chrome/browser/extensions/updater/extension_cache_impl.h
@@ -13,9 +13,9 @@
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "chrome/browser/extensions/updater/extension_cache.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
-#include "extensions/browser/updater/extension_cache.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
@@ -28,8 +28,7 @@ class LocalExtensionCache;
 class ExtensionCacheImpl : public ExtensionCache,
                            public content::NotificationObserver {
  public:
-  ExtensionCacheImpl();
-  virtual ~ExtensionCacheImpl();
+  static ExtensionCacheImpl* GetInstance();
 
   // Implementation of ExtensionCache.
   virtual void Start(const base::Closure& callback) override;
@@ -49,6 +48,11 @@ class ExtensionCacheImpl : public ExtensionCache,
                        const content::NotificationDetails& details) override;
 
  private:
+  friend struct DefaultSingletonTraits<ExtensionCacheImpl>;
+
+  ExtensionCacheImpl();
+  virtual ~ExtensionCacheImpl();
+
   // Callback that is called when local cache is ready.
   void OnCacheInitialized();