[ios] Moves tab_switcher code out of the ios_internal namespace.

ios/chrome/browser/ui/tab_switcher/session_changes.h

 // Copyright 2016 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_UI_TAB_SWITCHER_SESSION_CHANGES_H_
 #define IOS_CHROME_BROWSER_UI_TAB_SWITCHER_SESSION_CHANGES_H_
 
 #include <vector>
 
-namespace ios_internal {
-
 // This structure represents the changes a session undergoes.
 // It is used to update the UICollectionView showing a set of tabs.
 class SessionChanges {
  public:
   SessionChanges(std::vector<size_t> const& tabHashesInInitialState,
                  std::vector<size_t> const& tabHashesInFinalState);
   ~SessionChanges();
   SessionChanges(const SessionChanges& sessionChanges) = delete;
   SessionChanges& operator=(const SessionChanges& sessionChanges) = delete;
 
@@ skipping 12 matching lines @@
   // session.
   // -the indexes in |deletions| are relative to the previous state of the
   // session.
   // -the indexes in |insertions| are relative to the final state of the
   // session.
   std::vector<size_t> deletions_;
   std::vector<size_t> insertions_;
   std::vector<size_t> updates_;
 };
 
-}  // namespace ios_internal
-
 #endif  // IOS_CHROME_BROWSER_UI_TAB_SWITCHER_SESSION_CHANGES_H_