Avoid sending IDC_BACK/FORWARD when back/forward is not possible

ios/chrome/browser/ui/browser_view_controller.mm

Index: ios/chrome/browser/ui/browser_view_controller.mm
diff --git a/ios/chrome/browser/ui/browser_view_controller.mm b/ios/chrome/browser/ui/browser_view_controller.mm
index 3509d68559ea10667cee4be52299d5c63aa0d3fc..c3fda741f8dd394d6275c8392c8b7f1173f8d2f6 100644
--- a/ios/chrome/browser/ui/browser_view_controller.mm
+++ b/ios/chrome/browser/ui/browser_view_controller.mm
@@ -3548,6 +3548,14 @@ class BrowserBookmarkModelBridge : public bookmarks::BookmarkModelObserver {
   return [_model count];
 }
 
+- (BOOL)canGoBack {
+  return [_model currentTab].canGoBack;
+}
+
+- (BOOL)canGoForward {
+  return [_model currentTab].canGoForward;
+}
+
 - (void)focusTabAtIndex:(NSUInteger)index {
   if ([_model count] > index) {
     [_model setCurrentTab:[_model tabAtIndex:index]];
@@ -3914,9 +3922,7 @@ class BrowserBookmarkModelBridge : public bookmarks::BookmarkModelObserver {
 
   switch (command) {
     case IDC_BACK:
-      if ([_model currentTab].canGoBack) {
-        [[_model currentTab] goBack];
-      }
+      [[_model currentTab] goBack];
       break;
     case IDC_BOOKMARK_PAGE:
       [self initializeBookmarkInteractionController];
@@ -3957,9 +3963,7 @@ class BrowserBookmarkModelBridge : public bookmarks::BookmarkModelObserver {
       [self searchFindInPage];
       break;
     case IDC_FORWARD:
-      if ([_model currentTab].canGoForward) {
-        [[_model currentTab] goForward];
-      }
+      [[_model currentTab] goForward];
       break;
     case IDC_FULLSCREEN:
       NOTIMPLEMENTED();