Enforce the 'requirements' field in manifests.

chrome/browser/extensions/requirements_provider.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_REQUIREMENTS_PROVIDER_H_
+#define CHROME_BROWSER_EXTENSIONS_REQUIREMENTS_PROVIDER_H_
+
+#include <deque>
+#include <list>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/string16.h"
+#include "chrome/browser/extensions/extension_service.h"
+
+class ExtensionService;
+class GPUFeatureChecker;
+
+namespace extensions {
+class Extension;
+
+class RequirementsProvider {

[Aaron Boodman, 2012/07/22 17:46:25]

Since this class isn't 'providing' things right now, how about changing the name
to RequirementsChecker.

+ public:
+  RequirementsProvider();
+  ~RequirementsProvider();
+
+  // A false return is always valid, however a true one is only pending.
+  // ExtensionService::UnsupportedRequirements will be called on |service|
+  // if the requirements are not fullfilled. |async| will inform the caller
+  // if check is incomplete.
+  bool Supports(const Extension* extsnion, std::list<string16>* errors,

[Aaron Boodman, 2012/07/22 17:46:25]

This is a kind of odd interface. How about making it always provide the result
asynchronously, for consistency.

+                bool* async, ExtensionService* service);
+
+  // Answer all the pending requirement checks.
+  void IsWebGLAvailable(bool available);
+  void IsCSS3dAvailable(bool available);
+
+ private:
+  struct GPUFeatureRequest {
+    GPUFeatureRequest(const std::string& id,
+                      base::WeakPtr<ExtensionService> service);
+    GPUFeatureRequest();
+    ~GPUFeatureRequest();
+
+    std::string extension_id;
+    base::WeakPtr<ExtensionService> weak_service;
+  };
+
+  scoped_refptr<GPUFeatureChecker> webgl_checker_;
+  bool checked_for_webgl_;
+  bool webgl_supported_;
+  std::deque<GPUFeatureRequest> async_webgl_checks_;
+
+  scoped_refptr<GPUFeatureChecker> css3d_checker_;
+  bool checked_for_css3d_;
+  bool css3d_supported_;
+  std::deque<GPUFeatureRequest> async_css3d_checks_;
+
+  base::WeakPtrFactory<RequirementsProvider> weak_factory_;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_REQUIREMENTS_PROVIDER_H_