[SafeBrowsing] Block dangerous unchecked downloads based on a Finch trial.

chrome/browser/safe_browsing/unverified_download_policy.cc

+// Copyright 2015 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 "chrome/browser/safe_browsing/unverified_download_policy.h"
+
+#include "base/files/file_path.h"
+#include "base/metrics/sparse_histogram.h"
+#include "chrome/browser/safe_browsing/unverified_download_field_trial.h"
+#include "chrome/common/safe_browsing/download_protection_util.h"
+
+namespace safe_browsing {
+
+bool IsUnverifiedDownloadAllowed(const base::FilePath& file) {
+  // Currently, the policy is determined entirely by a field trial.
+  bool is_allowed = IsUnverifiedDownloadAllowedByFieldTrial(file);
+  int uma_file_type =
+      download_protection_util::GetSBClientDownloadExtensionValueForUMA(file);
+  if (is_allowed) {
+    UMA_HISTOGRAM_SPARSE_SLOWLY("SafeBrowsing.UnverifiedDownloads.Allowed",
+                                uma_file_type);
+  } else {
+    UMA_HISTOGRAM_SPARSE_SLOWLY("SafeBrowsing.UnverifiedDownloads.Blocked",
+                                uma_file_type);
+  }
+  return is_allowed;
+}
+
+}  // namespace safe_browsing