Put extension enable logic into a ExtensionEnableFlow.

chrome/browser/ui/extensions/extension_enable_flow_delegate.h

+// Copyright (c) 2012 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_UI_EXTENSIONS_EXTENSION_ENABLE_FLOW_DELEGATE_H_
+#define CHROME_BROWSER_UI_EXTENSIONS_EXTENSION_ENABLE_FLOW_DELEGATE_H_
+
+class ExtensionInstallPrompt;
+
+class ExtensionEnableFlowDelegate {
+ public:
+  // Invoked to create an ExtensionInstallPrompt for the flow to use. Caller
+  // takes ownership of the return ExtensionInstallPrompt;
+  virtual ExtensionInstallPrompt* CreateExtensionInstallPrompt() = 0;
+
+  // Invoked when |flow| is finished successfully.
+  virtual void ExtensionEnableFlowFinished() = 0;
+
+  // Invoked when |flow| is aborted.
+  virtual void ExtensionEnableFlowAborted(bool user_initiated) = 0;
+
+ protected:
+  virtual ~ExtensionEnableFlowDelegate() {}
+};
+
+#endif  // CHROME_BROWSER_UI_EXTENSIONS_EXTENSION_ENABLE_FLOW_DELEGATE_H_