[Offline pages] Resetting offline page metadata store to handle LOAD/INIT failures

components/offline_pages/offline_page_metadata_store.h

Index: components/offline_pages/offline_page_metadata_store.h
diff --git a/components/offline_pages/offline_page_metadata_store.h b/components/offline_pages/offline_page_metadata_store.h
index 26314804bdce08b2df6e0ad0280aee4937a3fb73..8613df7a9825c43aa53fb219386e3062960c4a05 100644
--- a/components/offline_pages/offline_page_metadata_store.h
+++ b/components/offline_pages/offline_page_metadata_store.h
@@ -38,16 +38,19 @@ class OfflinePageMetadataStore {
     LOAD_STATUS_COUNT
   };
 
-  typedef base::Callback<void(LoadStatus, const std::vector<OfflinePageItem>&)>
+  typedef base::Callback<void(const std::vector<OfflinePageItem>&)>
       LoadCallback;
+  typedef base::Callback<void(StoreState)> InitializeCallback;
   typedef base::Callback<void(ItemActionStatus)> AddCallback;
   typedef base::Callback<void(std::unique_ptr<OfflinePagesUpdateResult>)>
       UpdateCallback;
-  typedef base::Callback<void(bool)> ResetCallback;
 
   OfflinePageMetadataStore();
   virtual ~OfflinePageMetadataStore();
 
+  // Initializes the store. Should be called before any other methods.
+  virtual void Initialize(const InitializeCallback& callback) = 0;
+
   // Get all of the offline pages from the store.
   virtual void GetOfflinePages(const LoadCallback& callback) = 0;
 
@@ -65,7 +68,7 @@ class OfflinePageMetadataStore {
                                   const UpdateCallback& callback) = 0;
 
   // Resets the store.
-  virtual void Reset(const ResetCallback& callback) = 0;
+  virtual void Reset(const InitializeCallback& callback) = 0;
 
   // Gets the store state.
   virtual StoreState state() const = 0;