Use PreloadCheckGroup in ExtensionInstallChecker. Make RequirementsChecker a PreloadCheck.

chrome/browser/extensions/chrome_requirements_checker.h

-// Copyright (c) 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.
-
-#ifndef CHROME_BROWSER_EXTENSIONS_CHROME_REQUIREMENTS_CHECKER_H_
-#define CHROME_BROWSER_EXTENSIONS_CHROME_REQUIREMENTS_CHECKER_H_
-
-#include <vector>
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
-#include "extensions/browser/requirements_checker.h"
-
-namespace content {
-class GpuFeatureChecker;
-}
-
-namespace extensions {
-class Extension;
-
-// Validates the 'requirements' extension manifest field. This is an
-// asynchronous process that involves several threads, but the public interface
-// of this class (including constructor and destructor) must only be used on
-// the UI thread.
-class ChromeRequirementsChecker : public RequirementsChecker {
- public:
-  ChromeRequirementsChecker();
-  ~ChromeRequirementsChecker() override;
-
- private:
-  // RequirementsChecker:
-  void Check(const scoped_refptr<const Extension>& extension,
-             const RequirementsCheckedCallback& callback) override;
-
-  // Callbacks for the GpuFeatureChecker.
-  void SetWebGLAvailability(bool available);
-
-  void MaybeRunCallback();
-
-  std::vector<std::string> errors_;
-
-  // Every requirement that needs to be resolved asynchronously will add to
-  // this counter. When the counter is depleted, the callback will be run.
-  int pending_requirement_checks_;
-
-  scoped_refptr<content::GpuFeatureChecker> webgl_checker_;
-
-  RequirementsCheckedCallback callback_;
-
-  base::WeakPtrFactory<ChromeRequirementsChecker> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(ChromeRequirementsChecker);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_CHROME_REQUIREMENTS_CHECKER_H_