[ios] WebStateList owns all WebState it manages.

ios/chrome/browser/tabs/tab_model_unittest.mm

Index: ios/chrome/browser/tabs/tab_model_unittest.mm
diff --git a/ios/chrome/browser/tabs/tab_model_unittest.mm b/ios/chrome/browser/tabs/tab_model_unittest.mm
index 6b2a2d4b9e226dac553185863d9e2b26c816f66b..7a8f85a1e6205fdbceb8b59c1b51e7e8bc96306a 100644
--- a/ios/chrome/browser/tabs/tab_model_unittest.mm
+++ b/ios/chrome/browser/tabs/tab_model_unittest.mm
@@ -39,9 +39,6 @@
 #import "third_party/ocmock/OCMock/OCMock.h"
 #include "third_party/ocmock/gtest_support.h"
 
-using web::WebStateImpl;
-
-
 @interface TabModel (VisibleForTesting)
 - (SessionWindowIOS*)windowForSavingSession;
 @end
@@ -1064,21 +1061,6 @@ TEST_F(TabModelTest, MoveTabs) {
   [tab_model_ removeObserver:tab_model_observer.get()];
 }
 
-TEST_F(TabModelTest, SetParentModel) {
-  // Create a tab without a parent model and make sure it doesn't crash.  Then
-  // set its parent TabModel and make sure that works as well.
-  base::scoped_nsobject<Tab> tab([[Tab alloc]
-      initWithBrowserState:chrome_browser_state_.get()
-                    opener:nil
-               openedByDOM:NO
-                     model:nil]);
-  EXPECT_TRUE([tab parentTabModel] == nil);
-  [tab_model_ insertTab:tab atIndex:0];
-  [tab setParentTabModel:tab_model_.get()];
-  EXPECT_FALSE([tab parentTabModel] == nil);
-  [tab_model_ closeTabAtIndex:0];
-}
-
 TEST_F(TabModelTest, PersistSelectionChange) {
   NSString* stashPath =
       base::SysUTF8ToNSString(chrome_browser_state_->GetStatePath().value());