[ios] Refactor SessionServiceIOS to remove dependency on BrowserState.

ios/chrome/browser/sessions/session_service_ios.h

 // Copyright 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 IOS_CHROME_BROWSER_SESSIONS_SESSION_SERVICE_IOS_H_
 #define IOS_CHROME_BROWSER_SESSIONS_SESSION_SERVICE_IOS_H_
 
 #import <Foundation/Foundation.h>
 
-namespace ios {
-class ChromeBrowserState;
-}
+#include "base/sequenced_task_runner.h"
 
 @class SessionWindowIOS;
 
 // A singleton service for saving the current session. Can either save on a
 // delay or immediately. Saving is always performed on a separate thread.
 @interface SessionServiceIOS : NSObject
 
-// Lazily creates a singleton instance. Use this instead of calling alloc/init.
+// Lazily creates a singleton instance with a default task runner.
 + (SessionServiceIOS*)sharedService;
 
-// Saves the session represented by |window| to the given browserState directory
-// on disk. If |immediately| is NO, the save is done after a delay. If another
-// call is pending, this one is ignored. If YES, the save is done now,
-// cancelling any pending calls.  Either way, the save is done on a separate
-// thread to avoid blocking the UI thread. As a result, |window| should contain
-// copies of non-threadsafe objects.
-- (void)saveWindow:(SessionWindowIOS*)window
-    forBrowserState:(ios::ChromeBrowserState*)browserState
-        immediately:(BOOL)immediately;
+// Initializes a SessionServiceIOS with a given task runner. Prefer to use the
+// |sharedService| method.
+- (instancetype)initWithTaskRunner:
+    (const scoped_refptr<base::SequencedTaskRunner>&)taskRunner
+    NS_DESIGNATED_INITIALIZER;
 
-// Loads the window from the given browserState directory on disk on the main
-// thread. Returns nil if no session was previously saved.
-- (SessionWindowIOS*)loadWindowForBrowserState:
-    (ios::ChromeBrowserState*)browserState;
+// Saves the session represented by |sessionWindow| to |directory| on disk. If
+// |immediately| is NO, the save is done after a delay. If another call is
+// pending, this one is ignored. If YES, the save is done now, cancelling any
+// pending calls.  Either way, the save is done on a separate thread to avoid
+// blocking the UI thread.
+- (void)saveSessionWindow:(SessionWindowIOS*)sessionWindow
+                directory:(NSString*)directory
+              immediately:(BOOL)immediately;
 
-// Schedules deletion of the file containing the commands for the last session
-// in the given browserState directory.
-- (void)deleteLastSession:(NSString*)directory;
+// Loads the session window from default session file in |directory| on the
+// main thread. Returns nil in case of errors.
+- (SessionWindowIOS*)loadSessionWindowFromDirectory:(NSString*)directory;
 
-// Loads the window from the given backup file on disk on the main thread.
-// Returns nil if unable to read the sessions.
-- (SessionWindowIOS*)loadWindowFromPath:(NSString*)sessionPath;
+// Loads the session window from |sessionPath| on the main thread. Returns nil
+// in case of errors.
+- (SessionWindowIOS*)loadSessionWindowFromPath:(NSString*)sessionPath;
 
-// Returns the path of the session file.
-- (NSString*)sessionFilePathForDirectory:(NSString*)directory;
+// Schedules deletion of the file containing the last session in |directory|.
+- (void)deleteLastSessionFileInDirectory:(NSString*)directory;
+
+// Returns the path of the session file for |directory|.
++ (NSString*)sessionPathForDirectory:(NSString*)directory;
 
 @end
 
-@interface SessionServiceIOS (Testing)
+@interface SessionServiceIOS (SubClassing)
 
 // For some of the unit tests, we need to make sure the session is saved
 // immediately so we can read it back in to verify various attributes. This
 // is not a situation we normally expect to be in because we never
 // want the session being saved on the main thread in the production app.
-- (void)performSaveWindow:(SessionWindowIOS*)window
-              toDirectory:(NSString*)directory;
+- (void)performSaveSessionData:(NSData*)sessionData
+                   sessionPath:(NSString*)sessionPath;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_SESSIONS_SESSION_SERVICE_IOS_H_