[Extensions] Add missing include

chrome/browser/extensions/api/tabs/tabs_api_unittest.cc

 // 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.
 
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/api/tabs/tabs_api.h"
 #include "chrome/browser/extensions/extension_function_test_utils.h"
 #include "chrome/browser/extensions/extension_service_test_base.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/test/base/test_browser_window.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/common/browser_side_navigation_policy.h"
 #include "content/public/test/browser_side_navigation_test_utils.h"
 #include "content/public/test/web_contents_tester.h"
 #include "extensions/browser/api_test_utils.h"
+#include "extensions/common/constants.h"
 #include "extensions/common/extension_builder.h"
 #include "extensions/common/test_util.h"
 
 namespace extensions {
 
 namespace {
 
 std::unique_ptr<base::ListValue> RunTabsQueryFunction(
     Browser* browser,
     const Extension* extension,
@@ skipping 233 matching lines @@
   EXPECT_EQ(kGoogle, web_contents->GetVisibleURL());
 
   // Clean up.
   response_helper.WaitForResponse();
   while (!browser()->tab_strip_model()->empty())
     browser()->tab_strip_model()->CloseWebContentsAt(0, 0);
   base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace extensions