DownloadProtection: Add more graceful handling of verdict=UNKNOWN

chrome/browser/safe_browsing/download_protection_service.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.
 //
 // Helper class which handles communication with the SafeBrowsing servers for
 // improved binary download protection.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_DOWNLOAD_PROTECTION_SERVICE_H_
 #define CHROME_BROWSER_SAFE_BROWSING_DOWNLOAD_PROTECTION_SERVICE_H_
 
@@ skipping 169 matching lines @@
     REASON_DOWNLOAD_NOT_SUPPORTED = 17,
     REASON_INVALID_RESPONSE_VERDICT = 18,
     REASON_ARCHIVE_WITHOUT_BINARIES = 19,
     REASON_DOWNLOAD_DANGEROUS_HOST = 20,
     REASON_DOWNLOAD_POTENTIALLY_UNWANTED = 21,
     REASON_UNSUPPORTED_URL_SCHEME = 22,
     REASON_MANUAL_BLACKLIST = 23,
     REASON_LOCAL_FILE = 24,
     REASON_REMOTE_FILE = 25,
     REASON_SAMPLED_UNSUPPORTED_FILE = 26,
+    REASON_VERDICT_UNKNOWN = 27,
     REASON_MAX  // Always add new values before this one.
   };
 
  private:
   class CheckClientDownloadRequest;
   class PPAPIDownloadRequest;
   friend class DownloadProtectionServiceTest;
   friend class DownloadDangerPromptTest;
 
   FRIEND_TEST_ALL_PREFIXES(DownloadProtectionServiceTest,
@@ skipping 100 matching lines @@
   std::set<std::string> manual_blacklist_hashes_;
 
   // Rate of whitelisted downloads we sample to send out download ping.
   double whitelist_sample_rate_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadProtectionService);
 };
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_DOWNLOAD_PROTECTION_SERVICE_H_