extensions: Abstract out install delay strategy

chrome/browser/extensions/update_install_delayer.h

Index: chrome/browser/extensions/update_install_delayer.h
diff --git a/chrome/browser/extensions/update_install_delayer.h b/chrome/browser/extensions/update_install_delayer.h
new file mode 100644
index 0000000000000000000000000000000000000000..93c52f58f57b916515706504581fd389c57d1743
--- /dev/null
+++ b/chrome/browser/extensions/update_install_delayer.h
@@ -0,0 +1,33 @@
+// Copyright 2016 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_UPDATE_INSTALL_DELAYER_H_
+#define CHROME_BROWSER_EXTENSIONS_UPDATE_INSTALL_DELAYER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/extensions/install_delayer.h"
+
+class ExtensionService;
+
+namespace extensions {
+
+// Delays an extension update if the old version is not idle.
+class UpdateInstallDelayer : public InstallDelayer {
+ public:
+  explicit UpdateInstallDelayer(ExtensionService* service);
+
+  // InstallDelayer:
+  Action GetDelayedInstallAction(const Extension* extension,
+                                 bool install_immediately) override;
+
+ private:
+  // Not owned.
+  ExtensionService* const service_;
+
+  DISALLOW_COPY_AND_ASSIGN(UpdateInstallDelayer);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_UPDATE_INSTALL_DELAYER_H_