Add sampling of unknown filetypes in download protection.

chrome/common/safe_browsing/file_type_policies_test_util.h

Index: chrome/common/safe_browsing/file_type_policies_test_util.h
diff --git a/chrome/common/safe_browsing/file_type_policies_test_util.h b/chrome/common/safe_browsing/file_type_policies_test_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..7d6fd54ceb1bb3541321c44f34525eb72c3a1a7a
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+++ b/chrome/common/safe_browsing/file_type_policies_test_util.h
@@ -0,0 +1,41 @@
+// Copyright 2016 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_COMMON_SAFE_BROWSING_FILE_TYPE_POLICIES_TEST_UTIL_H_
+#define CHROME_COMMON_SAFE_BROWSING_FILE_TYPE_POLICIES_TEST_UTIL_H_
+
+#include "chrome/common/safe_browsing/file_type_policies.h"
+
+namespace safe_browsing {
+
+// This is a test fixture for modifying the proto with FileTypePolicies.
+// While an object of this class is in scope, it will cause callers
+// of FileTypePolicies::GetInstance() to see the modified list.
+// When it goes out of scope, future callers will get the original list.
+//
+// Example:
+//   FileTypePoliciesTestOverlay overlay_;
+//   std::unique_ptr<DownloadFileTypesConfig> cfg =
+//       overlay_.DuplicateConfig();
+//   cfg.set_sampled_ping_probability(1.0);
+//   overlay_.SwapConfig(cfg);
+//   ...
+class FileTypePoliciesTestOverlay {
+ public:
+  FileTypePoliciesTestOverlay();
+  ~FileTypePoliciesTestOverlay();
+
+  // Swaps the contents bewtween the existing config and |new_config|.
+  void SwapConfig(std::unique_ptr<DownloadFileTypeConfig>& new_config) const;
+
+  // Return a new copy of the original config.
+  std::unique_ptr<DownloadFileTypeConfig> DuplicateConfig() const;
+
+ private:
+  std::unique_ptr<DownloadFileTypeConfig> orig_config_;
+};
+
+}  // namespace safe_browsing
+
+#endif  // CHROME_COMMON_SAFE_BROWSING_FILE_TYPE_POLICIES_TEST_UTIL_H_