[ios] Refactor SessionServiceIOS to remove dependency on BrowserState.

ios/chrome/browser/tabs/tab_model.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/tabs/tab_model.h"
 
 #include <cstdint>
 #include <utility>
 #include <vector>
 
@@ skipping 344 matching lines @@
 
 - (BOOL)restoreSessionWindow:(SessionWindowIOS*)window {
   return [self restoreSessionWindow:window persistState:YES];
 }
 
 - (void)saveSessionImmediately:(BOOL)immediately {
   // Do nothing if there are tabs in the model but no selected tab. This is
   // a transitional state.
   if ((!self.currentTab && _webStateList->count()) || !_browserState)
     return;
-  [_sessionService saveWindow:self.windowForSavingSession
-              forBrowserState:_browserState
-                  immediately:immediately];
+  NSString* statePath =
+      base::SysUTF8ToNSString(_browserState->GetStatePath().AsUTF8Unsafe());
+  [_sessionService saveSessionWindow:self.windowForSavingSession
+                           directory:statePath
+                         immediately:immediately];
 }
 
 - (Tab*)tabAtIndex:(NSUInteger)index {
   DCHECK_LE(index, static_cast<NSUInteger>(INT_MAX));
   return LegacyTabHelper::GetTabForWebState(
       _webStateList->GetWebStateAt(static_cast<int>(index)));
 }
 
 - (NSUInteger)indexOfTab:(Tab*)tab {
   int index = _webStateList->GetIndexOfWebState(tab.webState);
@@ skipping 412 matching lines @@
 }
 
 // Called when UIApplicationWillEnterForegroundNotification is received.
 - (void)applicationWillEnterForeground:(NSNotification*)notify {
   if (_tabUsageRecorder) {
     _tabUsageRecorder->AppWillEnterForeground();
   }
 }
 
 @end