Revert "[ios] Ensure proper shutdown of Chrome on iOS."

ios/chrome/app/main_controller_unittest.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 <Foundation/Foundation.h>
 
 #include "base/threading/thread.h"
 #import "ios/chrome/app/application_delegate/app_state.h"
 #import "ios/chrome/app/application_delegate/url_opener.h"
 #include "ios/chrome/app/main_controller_private.h"
@@ skipping 38 matching lines @@
 // returns nothing.
 typedef void (^HandleLaunchOptions)(id self,
                                     NSDictionary* options,
                                     BOOL applicationActive,
                                     id<TabOpening> tabOpener,
                                     id<StartupInformation> startupInformation,
                                     AppState* appState);
 
 class TabOpenerTest : public PlatformTest {
  protected:
-  void TearDown() override {
-    [main_controller_ stopChromeMain];
-    PlatformTest::TearDown();
-  }
-
   BOOL swizzleHasBeenCalled() { return swizzle_block_executed_; }
 
   void swizzleHandleLaunchOptions(
       NSDictionary* expectedLaunchOptions,
       id<StartupInformation> expectedStartupInformation,
       AppState* expectedAppState) {
     swizzle_block_executed_ = NO;
     swizzle_block_ =
         [^(id self, NSDictionary* options, BOOL applicationActive,
            id<TabOpening> tabOpener, id<StartupInformation> startupInformation,
@@ skipping 68 matching lines @@
 
   // Action.
   [tabOpener openTabFromLaunchOptions:nil
                    startupInformation:startupInformationMock
                              appState:appStateMock];
 
   // Test.
   EXPECT_FALSE(swizzleHasBeenCalled());
 }
 }  // namespace