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

ios/chrome/browser/ui/tab_switcher/tab_switcher_model_unittest.mm

 // Copyright 2015 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.
 
 #include "ios/chrome/browser/ui/tab_switcher/tab_switcher_model.h"
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ios/chrome/browser/browser_state/test_chrome_browser_state.h"
@@ skipping 70 matching lines @@
   EXPECT_TRUE(insertedIndexes == _expectedSessionInserted.get() ||
               [insertedIndexes isEqualToArray:_expectedSessionInserted.get()]);
   _expectedSessionRemoved.reset();
   _expectedSessionInserted.reset();
 }
 
 - (void)distantSessionMayNeedUpdate:(std::string const&)tag {
   EXPECT_EQ(1UL, _expectedTagsOfTheSessionsNeedingUpdates.erase(tag));
 }
 
-- (void)localSessionMayNeedUpdate:(ios_internal::SessionType)type {
+- (void)localSessionMayNeedUpdate:(TabSwitcherSessionType)type {
   NOTREACHED();
 }
 
 - (void)signInPanelChangedTo:(TabSwitcherSignInPanelsType)panelType {
   NOTREACHED();
 }
 - (CGSize)sizeForItemAtIndex:(NSUInteger)index
-                   inSession:(ios_internal::SessionType)session {
+                   inSession:(TabSwitcherSessionType)session {
   return CGSizeZero;
 }
 @end
 
 namespace {
 
 class TabSwitcherModelTest : public PlatformTest {
  protected:
   void SetUp() override { delegate_.reset([[DelegateTester alloc] init]); }
 
@@ skipping 315 matching lines @@
   [delegate_ expectSessionsRemoved:@[ @1 ]];
   [delegate_ expectSessionsInserted:@[ @0 ]];
 
   [TabSwitcherModel notifyDelegate:delegate_
                    aboutChangeFrom:*old_sessions
                                 to:*new_sessions];
   [delegate_ verify];
 }
 
 }  // namespace