Remove POST data from navigations for which the state is replaced.

ios/web/navigation/crw_session_controller.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/web/navigation/crw_session_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 526 matching lines @@
 }
 
 - (void)updateCurrentEntryWithURL:(const GURL&)url
                       stateObject:(NSString*)stateObject {
   DCHECK(!_transientEntry);
   CRWSessionEntry* currentEntry = self.currentEntry;
   web::NavigationItemImpl* currentItem = self.currentEntry.navigationItemImpl;
   currentItem->SetURL(url);
   currentItem->SetSerializedStateObject(stateObject);
   currentItem->SetHasStateBeenReplaced(true);
+  currentItem->SetPostData(nil);
   currentEntry.navigationItem->SetURL(url);
   // If the change is to a committed entry, notify interested parties.
   if (currentEntry != self.pendingEntry && _navigationManager)
     _navigationManager->OnNavigationItemChanged();
 }
 
 - (void)discardNonCommittedEntries {
   [self discardTransientEntry];
   _pendingEntry.reset();
   _pendingEntryIndex = -1;
@@ skipping 185 matching lines @@
   return [[CRWSessionEntry alloc] initWithNavigationItem:std::move(item)];
 }
 
 - (BOOL)isRedirectTransitionForEntryAtIndex:(NSInteger)index {
   ui::PageTransition transition =
       [_entries[index] navigationItem]->GetTransitionType();
   return (transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) ? YES : NO;
 }
 
 @end