[ios] Remove IDC_BACK and IDC_FORWARD

ios/chrome/test/earl_grey/chrome_earl_grey.mm

Index: ios/chrome/test/earl_grey/chrome_earl_grey.mm
diff --git a/ios/chrome/test/earl_grey/chrome_earl_grey.mm b/ios/chrome/test/earl_grey/chrome_earl_grey.mm
index af378f1901843a9f9498ecf1b34f9d0ae28da017..71b4eaf5c1e2de843d3df80cb44b81f65550398c 100644
--- a/ios/chrome/test/earl_grey/chrome_earl_grey.mm
+++ b/ios/chrome/test/earl_grey/chrome_earl_grey.mm
@@ -122,16 +122,14 @@ id ExecuteJavaScript(NSString* javascript,
 }
 
 + (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];
 }