Adding a previews IO-thread blacklist

components/previews/core/previews_experiments.h

Index: components/previews/core/previews_experiments.h
diff --git a/components/previews/core/previews_experiments.h b/components/previews/core/previews_experiments.h
index 258f436e27fcf903535548e730772d73312a7ebe..9c8d7add0574d9a8f0a42d6a9bcdd75d41866221 100644
--- a/components/previews/core/previews_experiments.h
+++ b/components/previews/core/previews_experiments.h
@@ -1,19 +1,39 @@
 // 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 COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_
 #define COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_
 
+#include "base/time/time.h"
+
 namespace previews {
 
+namespace params {
+
+// The maximum number of recent previews navigations the black list looks at to
+// determine if a host is blacklisted.
+size_t MaxStoredHistoryLengthForBlackList();
+
+// The maximum number of hosts allowed in the in memory black list.
+size_t MaxInMemoryHostsInBlackList();
+
+// The number of recent navigations that were opted out of that would trigger
+// the host to be blacklisted.
+int BlackListOptOutThreshold();
+
+// The amount of time a host remains blacklisted due to opt outs.
+base::TimeDelta BlackListDuration();
+
+}  // namespace params
+
 // Returns true if any client-side previews experiment is active.
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial();
 
 // Returns true if the field trial that should enable offline pages for
 // prohibitvely slow networks is active.
 bool IsOfflinePreviewsEnabled();
 
 // Sets the appropriate state for field trial and variations to imitate the
 // offline pages field trial.
 bool EnableOfflinePreviewsForTesting();