Enforce the 'requirements' field in manifests.

chrome/browser/extensions/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_REQUIREMENTS_CHECKER_H_
+#define CHROME_BROWSER_EXTENSIONS_REQUIREMENTS_CHECKER_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/extensions/extension_service.h"
+
+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 RequirementsChecker : public base::SupportsWeakPtr<RequirementsChecker> {
+ public:
+  RequirementsChecker();
+  ~RequirementsChecker();
+
+  // The vector passed to the callback are any localized errors describing
+  // requirement violations. If this vector is non-empty, requirements checking
+  // failed. This should only be called once. |callback| will always be invoked
+  // asynchronously on the UI thread. |callback| will only be called once, and
+  // will be reset after called.
+  void Check(scoped_refptr<const Extension> extension,
+      base::Callback<void(std::vector<std::string> requirement)> callback);
+
+ private:
+  // Callbacks for the GPUFeatureChecker.
+  void SetWebGLAvailability(bool available);
+  void SetCSS3DAvailability(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<GPUFeatureChecker> webgl_checker_;
+  scoped_refptr<GPUFeatureChecker> css3d_checker_;
+
+  base::Callback<void(std::vector<std::string> requirement_errorss)> callback_;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_REQUIREMENTS_CHECKER_H_