Use PreloadCheckGroup in ExtensionInstallChecker. Make RequirementsChecker a PreloadCheck.

extensions/browser/preload_check.h

 // Copyright 2017 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 EXTENSIONS_BROWSER_PRELOAD_CHECK_H_
 #define EXTENSIONS_BROWSER_PRELOAD_CHECK_H_
 
 #include <memory>
 #include <unordered_set>
 #include <utility>
@@ skipping 10 matching lines @@
 // precondition holds for loading the given extension.
 class PreloadCheck {
  public:
   // These enumerators should only be referred to by name, so it is safe to
   // insert or remove values as necessary.
   enum Error {
     NONE,
     BLACKLISTED_ID,
     BLACKLISTED_UNKNOWN,
     DISALLOWED_BY_POLICY,
+    NPAPI_NOT_SUPPORTED,
+    WEBGL_NOT_SUPPORTED,
+    WINDOW_SHAPE_NOT_SUPPORTED,
   };
 
   // TODO(michaelpg): Remove std::hash<int> template argument once std::hash
   // directly supports enums.
   // See http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2148
   using Errors = std::unordered_set<Error, std::hash<int>>;
   using ResultCallback = base::OnceCallback<void(Errors)>;
 
   explicit PreloadCheck(scoped_refptr<const Extension> extension);
   virtual ~PreloadCheck();
@@ skipping 10 matching lines @@
  private:
   // The extension to check.
   scoped_refptr<const Extension> extension_;
 
   DISALLOW_COPY_AND_ASSIGN(PreloadCheck);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_PRELOAD_CHECK_H_