[ios] Remove IDC_BACK and IDC_FORWARD

ios/chrome/browser/web/cache_egtest.mm

 // 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.
 
 #import <EarlGrey/EarlGrey.h>
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/content_settings/core/common/content_settings.h"
@@ skipping 152 matching lines @@
   GenericChromeCommand* reloadCommand =
       [[GenericChromeCommand alloc] initWithTag:IDC_RELOAD];
   chrome_test_util::RunCommandWithActiveViewController(reloadCommand);
 
   [ChromeEarlGrey waitForPageToFinishLoading];
 }
 
 // Navigates back to the previous webpage.
 // TODO(crbug.com/638674): Evaluate if this can move to shared code.
 - (void)goBack {
-  GenericChromeCommand* backCommand =
-      [[GenericChromeCommand alloc] initWithTag:IDC_BACK];
-  chrome_test_util::RunCommandWithActiveViewController(backCommand);
+  [chrome_test_util::BrowserCommandDispatcherForMainBVC() goBack];
 
   [ChromeEarlGrey waitForPageToFinishLoading];
 }
 
 // Tests caching behavior on navigate back and page reload. Navigate back should
 // use the cached page. Page reload should use cache-control in the request
 // header and show updated page.
 - (void)testCachingBehaviorOnNavigateBackAndPageReload {
   web::test::SetUpHttpServer(base::MakeUnique<CacheTestResponseProvider>());
 
@@ skipping 73 matching lines @@
   [[EarlGrey
       selectElementWithMatcher:grey_accessibilityID(@"omnibox suggestion 1")]
       performAction:grey_tap()];
 
   // Verify title and hitCount. Cache should not be used.
   [ChromeEarlGrey waitForWebViewContainingText:"First Page"];
   [ChromeEarlGrey waitForWebViewContainingText:"serverHitCounter: 2"];
 }
 
 @end