[ios] Cleanup SessionServiceIOS implementation.

ios/chrome/browser/sessions/session_window_ios.mm

 // 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.
 
 #import "ios/chrome/browser/sessions/session_window_ios.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #import "base/mac/foundation_util.h"
 #import "ios/chrome/browser/sessions/NSCoder+Compatibility.h"
@@ skipping 31 matching lines @@
   DCHECK(sessions);
   DCHECK(IsIndexValidForSessionCount(selectedIndex, [sessions count]));
   self = [super init];
   if (self) {
     _sessions = [sessions copy];
     _selectedIndex = selectedIndex;
   }
   return self;
 }
 
-- (void)clearSessions {
-  _sessions = @[];
-  _selectedIndex = NSNotFound;
-}
-
 #pragma mark - NSCoding
 
 - (instancetype)initWithCoder:(NSCoder*)aDecoder {
   NSUInteger selectedIndex = [aDecoder cr_decodeIndexForKey:kSelectedIndexKey];
   NSArray<CRWSessionStorage*>* sessions =
       base::mac::ObjCCast<NSArray<CRWSessionStorage*>>(
           [aDecoder decodeObjectForKey:kSessionsKey]);
 
   if (!sessions) {
     sessions = @[];
@@ skipping 17 matching lines @@
 
 #pragma mark - Debugging
 
 - (NSString*)description {
   return [NSString stringWithFormat:@"selected index: %" PRIuNS
                                      "\nsessions:\n%@\n",
                                     _selectedIndex, _sessions];
 }
 
 @end