[iOS] Upstream chrome commands

ios/chrome/browser/ui/commands/generic_chrome_command.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 "ios/chrome/browser/ui/commands/generic_chrome_command.h"
+
+#import <UIKit/UIKit.h>
+
+#include "base/logging.h"
+#import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
+
+@implementation GenericChromeCommand {
+  NSInteger _tag;
+}
+
+@synthesize tag = _tag;
+
+- (instancetype)init {
+  return [self initWithTag:0];
+}
+
+- (instancetype)initWithTag:(NSInteger)tag {
+  self = [super init];
+  if (self) {
+    _tag = tag;
+  }
+  return self;
+}
+
+- (void)executeOnMainWindow {
+  UIWindow* mainWindow = [[UIApplication sharedApplication] keyWindow];
+  DCHECK(mainWindow);
+  [mainWindow chromeExecuteCommand:self];
+}
+
+@end