[ios] Remove IDC_BACK and IDC_FORWARD

ios/chrome/test/earl_grey/chrome_earl_grey.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 "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 
 #import <Foundation/Foundation.h>
 #import <WebKit/WebKit.h>
 
 #include "base/mac/foundation_util.h"
@@ skipping 104 matching lines @@
 }
 
 + (void)reload {
   base::scoped_nsobject<GenericChromeCommand> reloadCommand(
       [[GenericChromeCommand alloc] initWithTag:IDC_RELOAD]);
   chrome_test_util::RunCommandWithActiveViewController(reloadCommand);
   [ChromeEarlGrey waitForPageToFinishLoading];
 }
 
 + (void)goBack {
-  base::scoped_nsobject<GenericChromeCommand> reloadCommand(
-      [[GenericChromeCommand alloc] initWithTag:IDC_BACK]);
-  chrome_test_util::RunCommandWithActiveViewController(reloadCommand);
+  [chrome_test_util::BrowserCommandDispatcherForMainBVC() goBack];
+
   [ChromeEarlGrey waitForPageToFinishLoading];
 }
 
 + (void)goForward {
-  base::scoped_nsobject<GenericChromeCommand> reloadCommand(
-      [[GenericChromeCommand alloc] initWithTag:IDC_FORWARD]);
-  chrome_test_util::RunCommandWithActiveViewController(reloadCommand);
+  [chrome_test_util::BrowserCommandDispatcherForMainBVC() goForward];
+
   [ChromeEarlGrey waitForPageToFinishLoading];
 }
 
 + (void)waitForPageToFinishLoading {
   GREYCondition* condition =
       [GREYCondition conditionWithName:@"Wait for page to complete loading."
                                  block:^BOOL {
                                    return !chrome_test_util::IsLoading();
                                  }];
   GREYAssert([condition waitWithTimeout:testing::kWaitForPageLoadTimeout],
@@ skipping 53 matching lines @@
   GREYCondition* condition = [GREYCondition
       conditionWithName:@"Wait for web view not containing text"
                   block:^BOOL {
                     return !web::test::IsWebViewContainingText(
                         chrome_test_util::GetCurrentWebState(), text);
                   }];
   GREYAssert([condition waitWithTimeout:testing::kWaitForUIElementTimeout],
              @"Failed waiting for web view not containing %s", text.c_str());
 }
 @end