[Downloads] Gracefully handle SafeBrowsing check failures.

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 23 matching lines @@
 
 namespace safe_browsing {
 class DownloadFeedbackService;
 class BinaryFeatureExtractor;
 
 // This class provides an asynchronous API to check whether a particular
 // client download is malicious or not.
 class DownloadProtectionService {
  public:
   enum DownloadCheckResult {
+    UNKNOWN,
     SAFE,
     DANGEROUS,
     UNCOMMON,
     DANGEROUS_HOST,
     POTENTIALLY_UNWANTED
   };
 
   // Callback type which is invoked once the download request is done.
   typedef base::Callback<void(DownloadCheckResult)> CheckDownloadCallback;
 
@@ skipping 29 matching lines @@
 
   // Display more information to the user regarding the download specified by
   // |info|. This method is invoked when the user requests more information
   // about a download that was marked as malicious.
   void ShowDetailsForDownload(const content::DownloadItem& item,
                               content::PageNavigator* navigator);
 
   // Enables or disables the service.  This is usually called by the
   // SafeBrowsingService, which tracks whether any profile uses these services
   // at all.  Disabling causes any pending and future requests to have their
-  // callbacks called with "SAFE" results.
+  // callbacks called with "UNKNOWN" results.
   void SetEnabled(bool enabled);
 
   bool enabled() const {
     return enabled_;
   }
 
   // Returns the timeout that is used by CheckClientDownload().
   int64 download_request_timeout_ms() const {
     return download_request_timeout_ms_;
   }
@@ skipping 91 matching lines @@
 
   int64 download_request_timeout_ms_;
 
   scoped_ptr<DownloadFeedbackService> feedback_service_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadProtectionService);
 };
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_DOWNLOAD_PROTECTION_SERVICE_H_