Remove extension-to-component migration mechanism

chrome/browser/extensions/component_migration_helper.h

Index: chrome/browser/extensions/component_migration_helper.h
diff --git a/chrome/browser/extensions/component_migration_helper.h b/chrome/browser/extensions/component_migration_helper.h
deleted file mode 100644
index 2e78b5ee736466286d45311fecdfeb0339a9c6cc..0000000000000000000000000000000000000000
--- a/chrome/browser/extensions/component_migration_helper.h
+++ /dev/null
@@ -1,148 +0,0 @@
-// 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_COMPONENT_MIGRATION_HELPER_H_
-#define CHROME_BROWSER_EXTENSIONS_COMPONENT_MIGRATION_HELPER_H_
-
-#include <set>
-#include <string>
-#include <utility>
-#include <vector>
-
-#include "base/macros.h"
-#include "base/scoped_observer.h"
-#include "extensions/browser/extension_registry_observer.h"
-
-class Profile;
-class PrefRegistrySimple;
-class PrefService;
-
-namespace content {
-class BrowserContext;
-}
-
-namespace extensions {
-
-class ExtensionRegistry;
-class ExtensionSystem;
-
-// For migrating existing extensions to component actions, and vice versa.  A
-// previous enabled extension is used as a signal to add the corresponding
-// component action to the visible area of the toolbar. This allows users who
-// have already installed the extension to have their preference for a component
-// action in the visible area of the toolbar respected, without enabling this
-// for the entire user base.
-//
-// MIGRATION LOGIC
-//
-// When the feature is enabled (i.e. by experiment or flag), the client should
-// call OnFeatureEnabled(action_id).  The extension action redesign MUST also be
-// enabled.
-//
-//   - If the extension is enabled, it is unloaded with a reason of
-//     MIGRATED_TO_COMPONENT, the component action shown, and a pref set
-//     recording the migration.
-//   - If pref is set the component action is shown.
-//   - Otherwise, the component action is not shown.
-//
-// When the feature is disabled (for example, by starting with a flag off), the
-// client should call OnFeatureDisabled(action_id).
-//
-//   - The pref is removed.
-//   - If the extension action redesign is enabled, the associated component
-//     action is removed.
-//
-// USAGE
-// helper->Register("some-action-id", "some-extension-id");
-// helper->Register("some-action-id", "other-extension-id");
-// ...
-// // When feature is enabled
-// helper->OnFeatureEnabled("some-action-id");
-// ...
-// // When feature is disabled
-// helper->OnFeatureDisabled("some-action-id");
-//
-// It is legal to register more than one extension per action but not vice
-// versa.
-class ComponentMigrationHelper : public ExtensionRegistryObserver {
- public:
-  // Object that knows how to manage component actions in the toolbar model.
-  class ComponentActionDelegate {
-   public:
-    // Adds or removes the component action labeled by |action_id| from the
-    // toolbar model.  The caller will not add the same action twice.
-    virtual void AddComponentAction(const std::string& action_id) = 0;
-    virtual void RemoveComponentAction(const std::string& action_id) = 0;
-
-    // Returns |true| if the toolbar model has an action for |action_id|.
-    virtual bool HasComponentAction(const std::string& action_id) const = 0;
-  };
-
-  ComponentMigrationHelper(Profile* profile, ComponentActionDelegate* delegate);
-  ~ComponentMigrationHelper() override;
-
-  static void RegisterPrefs(PrefRegistrySimple* registry);
-
-  // Registers and unregisters a component action/extension pair.  A component
-  // action may have more than one associated extension id, but not vice versa.
-  void Register(const std::string& component_action_id,
-                const ExtensionId& extension_id);
-  void Unregister(const std::string& component_action_id,
-                  const ExtensionId& extension_id);
-
-  // Call when we should potentially add the component action and unload
-  // the extension.  PREREQUISITE: The extension action redesign MUST be
-  // enabled.
-  void OnFeatureEnabled(const std::string& component_action_id);
-
-  // Call when we should potentially remove the component action and re-enable
-  // extension loading.
-  void OnFeatureDisabled(const std::string& component_action_id);
-
-  // Call when the user manually removes the component action from the toolbar.
-  void OnActionRemoved(const std::string& component_action_id);
-
-  // extensions::ExtensionRegistryObserver:
-  void OnExtensionReady(content::BrowserContext* browser_context,
-                        const Extension* extension) override;
-
-  // Gets and sets the preference for whether to put the component action with
-  // the given ID on the toolbar (or in the overflow menu).
-  // GetComponentActionPref() returns false if the pref has not been set.
-  bool GetComponentActionPref(const std::string& component_action_id) const;
-  void SetComponentActionPref(const std::string& component_action_id,
-                              bool enabled);
-
- protected:
-  // A set of component action ids whose features are currently enabled.
-  // Protected for unit testing.
-  std::set<std::string> enabled_actions_;
-
- private:
-  bool IsExtensionInstalledAndEnabled(const ExtensionId& extension_id) const;
-  void UnloadExtension(const ExtensionId& extension_id);
-  void RemoveComponentActionPref(const std::string& component_action_id);
-  std::vector<std::string> GetExtensionIdsForActionId(
-      const std::string& component_action_id) const;
-  std::string GetActionIdForExtensionId(const ExtensionId& extension_id) const;
-
-  ComponentActionDelegate* const delegate_;
-  // The ExtensionRegistry, PrefService, and ExtensionSystem, cached for
-  // convenience.
-  ExtensionRegistry* const extension_registry_;
-  PrefService* const pref_service_;
-  ExtensionSystem* const extension_system_;
-
-  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
-      extension_registry_observer_;
-
-  // A list of pairs of component action ids and extension ids.
-  std::vector<std::pair<std::string, ExtensionId>> migrated_actions_;
-
-  DISALLOW_COPY_AND_ASSIGN(ComponentMigrationHelper);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_COMPONENT_MIGRATION_HELPER_H_