Move InMemoryURLIndex Caching Operations to FILE Thread

chrome/browser/history/in_memory_url_index.h

Index: chrome/browser/history/in_memory_url_index.h
===================================================================
--- chrome/browser/history/in_memory_url_index.h	(revision 125451)
+++ chrome/browser/history/in_memory_url_index.h	(working copy)
@@ -15,8 +15,8 @@
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "base/string16.h"
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/autocomplete/history_provider_util.h"
@@ -24,7 +24,6 @@
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/history/in_memory_url_index_types.h"
-#include "chrome/browser/history/in_memory_url_index_cache.pb.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "sql/connection.h"
@@ -45,6 +44,7 @@
 namespace imui = in_memory_url_index;
 
 class HistoryDatabase;
+class RefCountedURLIndexPrivateDataPtr;
 class URLIndexPrivateData;
 struct URLVisitedDetails;
 struct URLsModifiedDetails;
@@ -69,8 +69,33 @@
 // will eliminate such words except in the case where a single character
 // is being searched on and which character occurs as the second char16 of a
 // multi-char16 instance.
-class InMemoryURLIndex : public content::NotificationObserver {
+class InMemoryURLIndex : public content::NotificationObserver,
+                         public base::SupportsWeakPtr<InMemoryURLIndex> {
  public:
+  // Defines an abstract class which is notified upon completion of restoring
+  // the index's private data either by reading from the cache file or by
+  // rebuilding from the history database.
+  class RestoreCacheObserver {
+   public:
+    virtual ~RestoreCacheObserver();
+
+    // Callback that lets the observer know that the restore operation has
+    // completed. |succeeded| indicates if the restore was successful. This is
+    // called on the UI thread.
+    virtual void OnCacheRestoreFinished(bool succeeded) = 0;
+  };
+
+  // Defines an abstract class which is notified upon completion of saving
+  // the index's private data to the cache file.
+  class SaveCacheObserver {
+   public:
+    virtual ~SaveCacheObserver();
+
+    // Callback that lets the observer know that the save succeeded.
+    // This is called on the UI thread.
+    virtual void OnCacheSaveFinished(bool succeeded) = 0;
+  };
+
   // |profile|, which may be NULL during unit testing, is used to register for
   // history changes. |history_dir| is a path to the directory containing the
   // history database within the profile wherein the cache and transaction
@@ -96,11 +121,21 @@
   // refer to that class.
   ScoredHistoryMatches HistoryItemsForTerms(const string16& term_string);
 
+  // Sets the optional observers for completion of restoral and saving of the
+  // index's private data.
+  void set_restore_cache_observer(
+      RestoreCacheObserver* restore_cache_observer) {
+    restore_cache_observer_ = restore_cache_observer;
+  }
+  void set_save_cache_observer(SaveCacheObserver* save_cache_observer) {
+    save_cache_observer_ = save_cache_observer;
+  }
+
  private:
   friend class ::HistoryQuickProviderTest;
   friend class InMemoryURLIndexTest;
+  friend class InMemoryURLIndexCacheTest;
   FRIEND_TEST_ALL_PREFIXES(LimitedInMemoryURLIndexTest, Initialization);
-  FRIEND_TEST_ALL_PREFIXES(InMemoryURLIndexCacheTest, CacheFilePath);
 
   // Creating one of me without a history path is not allowed (tests excepted).
   InMemoryURLIndex();
@@ -133,14 +168,14 @@
   // provided as a hook for unit testing.)
   bool GetCacheFilePath(FilePath* file_path);
 
+  // Sets the directory wherein the cache file will be maintained.
+  // For unit test usage only.
+  void set_history_dir(const FilePath& dir_path) { history_dir_ = dir_path; }
+
   // Restores the index's private data from the cache file stored in the
   // profile directory.
-  void RestoreFromCacheFile();
+  void PostRestoreFromCacheFileTask();
 
-  // Restores private_data_ from the given |path|. Runs on the UI thread.
-  // Provided for unit testing so that a test cache file can be used.
-  void DoRestoreFromCacheFile(const FilePath& path);
-
   // Schedules a history task to rebuild our private data from the history
   // database.
   void ScheduleRebuildFromHistory();
@@ -155,14 +190,42 @@
   // Used for unit testing only.
   void RebuildFromHistory(HistoryDatabase* history_db);
 
-  // Caches the index private data and writes the cache file to the profile
-  // directory.
-  void SaveToCacheFile();
+  // Posts a task to cache the index private data and write the cache file to
+  // the profile directory.
+  void PostSaveToCacheFileTask();
 
   // Saves private_data_ to the given |path|. Runs on the UI thread.
   // Provided for unit testing so that a test cache file can be used.
   void DoSaveToCacheFile(const FilePath& path);
 
+  // Notifies the observer, if any, of the success of the private data caching.
+  // |succeeded| is true on a successful save.
+  void OnCacheSaveDone(scoped_refptr<RefCountedBool> succeeded);
+
+  // Callback used by RebuildPrivateDataFromHistoryDBTask to signal completion
+  // or rebuilding our private data from the history database. |succeeded|
+  // will be true if the rebuild was successful. |data| will point to a new
+  // instanceof the private data just rebuilt.
+  void DoneRebuidingPrivateDataFromHistoryDB(bool succeeded,
+                                             URLIndexPrivateData* data);
+
+  // Rebuilds the history index from the history database in |history_db|.
+  // Used for unit testing only.
+  void RebuildFromHistory(URLDatabase* history_db);
+
+  // Determines if the private data was successfully reloaded from the cache
+  // file or if the private data must be rebuilt from the history database.
+  // |private_data_ptr|'s data will be NULL if the cache file load failed.
+  void OnCacheLoadDone(
+    scoped_refptr<RefCountedURLIndexPrivateDataPtr> private_data_ptr);
+
+  // Callback function that sets the private data from the just-restored-from-
+  // file |private_data| if |succeeded| otherwise clears the private data.
+  // Notifies any |restore_cache_observer_| of success status.
+  void OnCacheRestored(URLIndexPrivateData* private_data, bool succeeded);
+
+  // Notifications -------------------------------------------------------------
+
   // Handles notifications of history changes.
   virtual void Observe(int notification_type,
                        const content::NotificationSource& source,
@@ -187,12 +250,16 @@
   // The index's durable private data.
   scoped_ptr<URLIndexPrivateData> private_data_;
 
-  // Set to true once the shutdown process has begun.
-  bool shutdown_;
+  // Observers to notify upon restoral or save of the private data cache.
+  RestoreCacheObserver* restore_cache_observer_;
+  SaveCacheObserver* save_cache_observer_;
 
   CancelableRequestConsumer cache_reader_consumer_;
   content::NotificationRegistrar registrar_;
 
+  // Set to true once the shutdown process has begun.
+  bool shutdown_;
+
   // Set to true when changes to the index have been made and the index needs
   // to be cached. Set to false when the index has been cached. Used as a
   // temporary safety check to insure that the cache is saved before the