app_list: Refactor mixer groups to avoid hard-coded groups in Mixer.

ui/app_list/search_controller.h

 // Copyright 2013 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 UI_APP_LIST_SEARCH_CONTROLLER_H_
 #define UI_APP_LIST_SEARCH_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
@@ skipping 21 matching lines @@
   virtual ~SearchController();
 
   void Start(bool is_voice_query);
   void Stop();
 
   void OpenResult(SearchResult* result, int event_flags);
   void InvokeResultAction(SearchResult* result,
                           int action_index,
                           int event_flags);
 
+  // Adds a new mixer group. See Mixer::AddGroup.
+  size_t AddGroup(size_t max_results, double boost);
+
   // Takes ownership of |provider| and associates it with given mixer group.
-  void AddProvider(Mixer::GroupId group,
-                   scoped_ptr<SearchProvider> provider);
+  void AddProvider(size_t group_id, scoped_ptr<SearchProvider> provider);
 
  private:
   typedef ScopedVector<SearchProvider> Providers;
 
   // Invoked when the search results are changed.
   void OnResultsChanged();
 
   SearchBoxModel* search_box_;
 
   bool dispatching_query_;
   Providers providers_;
   scoped_ptr<Mixer> mixer_;
   History* history_;  // KeyedService, not owned.
 
   bool is_voice_query_;
 
   base::OneShotTimer<SearchController> stop_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(SearchController);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_SEARCH_CONTROLLER_H_