PreloadCheck class for extension pre-install checks

extensions/browser/preload_check.h

Index: extensions/browser/preload_check.h
diff --git a/extensions/browser/preload_check.h b/extensions/browser/preload_check.h
new file mode 100644
index 0000000000000000000000000000000000000000..116bd3cd3980fad6f50ffa62375afd1efcac13f3
--- /dev/null
+++ b/extensions/browser/preload_check.h
@@ -0,0 +1,61 @@
+// 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>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "extensions/common/constants.h"

[Devlin, 2017/03/08 03:01:47]

needed?

[michaelpg, 2017/03/09 01:53:30]

Removed.

+#include "extensions/common/extension.h"
+
+namespace extensions {
+
+// Encapsulates a possibly asynchronous operation to verify whether a
+// 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,
+  };
+
+  // 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
+  typedef std::unordered_set<Error, std::hash<int>> Errors;

[Devlin, 2017/03/08 03:01:46]

prefer using x = foo syntax in new code.

[michaelpg, 2017/03/09 01:53:30]

TIL, done

+
+  typedef base::OnceCallback<void(Errors)> ResultCallback;
+
+  explicit PreloadCheck(const Extension* extension) : extension_(extension) {}
+  virtual ~PreloadCheck() {}
+
+  // This function must be called on the UI thread. The callback also occurs on
+  // the UI thread.
+  virtual void Start(ResultCallback callback) = 0;
+
+  // Subclasses that provide an error message should return |true|.
+  virtual bool GetErrorMessage(base::string16* error) const;
+
+  const Extension* extension() { return extension_; }
+
+ private:
+  // The extension to check.
+  const Extension* extension_;

[Devlin, 2017/03/08 03:01:48]

We should refcount this.

[michaelpg, 2017/03/09 01:53:30]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(PreloadCheck);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_PRELOAD_CHECK_H_