Revert "Move ExtensionCache to //extensions"

chrome/browser/extensions/updater/extension_cache.cc

Index: chrome/browser/extensions/updater/extension_cache.cc
diff --git a/chrome/browser/extensions/updater/extension_cache.cc b/chrome/browser/extensions/updater/extension_cache.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c9111c7897911b6271fdb62e8c37b63ba5f1a286
--- /dev/null
+++ b/chrome/browser/extensions/updater/extension_cache.cc
@@ -0,0 +1,84 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/extensions/updater/extension_cache.h"
+
+#include "base/memory/singleton.h"
+
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/extensions/updater/extension_cache_impl.h"
+#endif  // OS_CHROMEOS
+
+namespace extensions {
+namespace {
+
+#if !defined(OS_CHROMEOS)
+
+// Implementation of ExtensionCache that doesn't cache anything.
+// Real cache is used only on Chrome OS other OSes use this null implementation.
+class ExtensionCacheNullImpl : public ExtensionCache {
+ public:
+  static ExtensionCacheNullImpl* GetInstance() {
+    return Singleton<ExtensionCacheNullImpl>::get();
+  }
+
+  // Implementation of ExtensionCache.
+  virtual void Start(const base::Closure& callback) override {
+    callback.Run();
+  }
+
+  virtual void Shutdown(const base::Closure& callback) override {
+    callback.Run();
+  }
+
+  virtual void AllowCaching(const std::string& id) override {
+  }
+
+  virtual bool GetExtension(const std::string& id,
+                            base::FilePath* file_path,
+                            std::string* version) override {
+    return false;
+  }
+
+  virtual void PutExtension(const std::string& id,
+                            const base::FilePath& file_path,
+                            const std::string& version,
+                            const PutExtensionCallback& callback) override {
+    callback.Run(file_path, true);
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<ExtensionCacheNullImpl>;
+
+  ExtensionCacheNullImpl() {}
+  virtual ~ExtensionCacheNullImpl() {}
+};
+
+#endif  // !OS_CHROMEOS
+
+static ExtensionCache* g_extension_cache_override = NULL;
+
+}  // namespace
+
+// static
+ExtensionCache* ExtensionCache::GetInstance() {
+  if (g_extension_cache_override) {
+    return g_extension_cache_override;
+  } else {
+#if defined(OS_CHROMEOS)
+    return ExtensionCacheImpl::GetInstance();
+#else
+    return ExtensionCacheNullImpl::GetInstance();
+#endif
+  }
+}
+
+// static
+ExtensionCache* ExtensionCache::SetForTesting(ExtensionCache* cache) {
+  ExtensionCache* temp = g_extension_cache_override;
+  g_extension_cache_override = cache;
+  return temp;
+}
+
+}  // namespace extensions