[Downloads] Gracefully handle SafeBrowsing check failures.

chrome/browser/download/chrome_download_manager_delegate.cc

Index: chrome/browser/download/chrome_download_manager_delegate.cc
diff --git a/chrome/browser/download/chrome_download_manager_delegate.cc b/chrome/browser/download/chrome_download_manager_delegate.cc
index 296ae5e45ccb13d71d1d493e5ea4f4cea1e168a4..1876f08e57daa233f73576514e1deadaf49a6aca 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -159,7 +159,8 @@ void CheckDownloadUrlDone(
     bool is_content_check_supported,
     DownloadProtectionService::DownloadCheckResult result) {
   content::DownloadDangerType danger_type;
-  if (result == DownloadProtectionService::SAFE) {
+  if (result == DownloadProtectionService::SAFE ||
+      result == DownloadProtectionService::UNKNOWN) {
     // If this type of files is handled by the enhanced SafeBrowsing download
     // protection, mark it as potentially dangerous content until we are done
     // with scanning it.
@@ -636,6 +637,11 @@ void ChromeDownloadManagerDelegate::CheckClientDownloadDone(
     content::DownloadDangerType danger_type =
         content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS;
     switch (result) {
+      case DownloadProtectionService::UNKNOWN:
+        // The check failed or was inconclusive.
+        if (DownloadItemModel(item).IsDangerousFileBasedOnType())
+          danger_type = content::DOWNLOAD_DANGER_TYPE_DANGEROUS_FILE;
+        break;
       case DownloadProtectionService::SAFE:
         // Do nothing.
         break;
@@ -688,10 +694,15 @@ void ChromeDownloadManagerDelegate::OnDownloadTargetDetermined(
     scoped_ptr<DownloadTargetInfo> target_info) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DownloadItem* item = download_manager_->GetDownload(download_id);
-  if (!target_info->target_path.empty() && item &&
-      IsOpenInBrowserPreferreredForFile(target_info->target_path) &&
-      target_info->is_filetype_handled_safely)
-    DownloadItemModel(item).SetShouldPreferOpeningInBrowser(true);
+  if (item) {
+    if (!target_info->target_path.empty() &&
+        IsOpenInBrowserPreferreredForFile(target_info->target_path) &&
+        target_info->is_filetype_handled_safely)
+      DownloadItemModel(item).SetShouldPreferOpeningInBrowser(true);
+
+    if (target_info->is_dangerous_file)
+      DownloadItemModel(item).SetIsDangerousFileBasedOnType(true);
+  }
   callback.Run(target_info->target_path,
                target_info->target_disposition,
                target_info->danger_type,