PreloadCheck class for extension pre-install checks

extensions/browser/policy_check.cc

+// 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.
+
+#include "extensions/browser/policy_check.h"
+
+#include "content/public/browser/browser_context.h"
+#include "extensions/browser/extension_system.h"
+#include "extensions/browser/management_policy.h"
+
+namespace extensions {
+
+PolicyCheck::PolicyCheck(content::BrowserContext* context,
+                         const Extension* extension)
+    : PreloadCheck(extension), context_(context) {}
+
+PolicyCheck::~PolicyCheck() {}
+
+void PolicyCheck::Start(ResultCallback callback) {
+  Errors errors;
+  if (!ExtensionSystem::Get(context_)->management_policy()->UserMayLoad(
+          extension(), &error_)) {
+    DCHECK(!error_.empty());
+    errors.insert(DISALLOWED_BY_POLICY);
+  }
+  std::move(callback).Run(errors);
+}
+
+bool PolicyCheck::GetErrorMessage(base::string16* error) const {
+  if (!error || !error_.size())

[Devlin, 2017/03/08 03:01:45]

Why do we want to handle null string16 pointers?  Seems like something we
shouldn't allow.

I also wouldn't be opposed to just returning a base::string16 and using empty to
signify no error, but it's hard to say without a bit more context.

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

you're right, that seems pointless, and it's unclear whether that case would
return true or false.
That's definitely simpler. Not sure what my motivation was for this.

+    return false;
+  *error = error_;
+  return true;
+}
+
+}  // namespace extensions