Implement host-based deletion for the hostname resolution cache.

net/dns/host_cache.cc

 // 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.
 
 #include "net/dns/host_cache.h"
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 180 matching lines @@
 void HostCache::OnNetworkChange() {
   ++network_changes_;
 }
 
 void HostCache::clear() {
   DCHECK(CalledOnValidThread());
   RecordEraseAll(ERASE_CLEAR, base::TimeTicks::Now());
   entries_.clear();
 }
 
+void HostCache::ClearForHosts(
+    const base::Callback<bool(const std::string&)>& host_filter) {
+  DCHECK(CalledOnValidThread());
+
+  if (host_filter.is_null()) {
+    clear();
+    return;
+  }
+
+  for (EntryMap::iterator it = entries_.begin(); it != entries_.end();) {
+    EntryMap::iterator next_it = std::next(it);
+
+    if (host_filter.Run(it->first.hostname)) {
+      RecordErase(ERASE_CLEAR, base::TimeTicks::Now(), it->second);

[mmenke, 2016/08/31 15:24:37]

Maybe just call base::TimeTicks::Now() once, outside of the loop?  Not sure how
expensive it is, and this is called rarely enough that it probably doesn't
really matter, but does seem like we don't need to keep on getting the time.

[msramek, 2016/08/31 16:02:55]

Done. Good point - it's even better for consistency, as clear() also uses the
same timestamp for all entries.

+      entries_.erase(it);
+    }
+
+    it = next_it;
+  }
+}
+
 size_t HostCache::size() const {
   DCHECK(CalledOnValidThread());
   return entries_.size();
 }
 
 size_t HostCache::max_entries() const {
   DCHECK(CalledOnValidThread());
   return max_entries_;
 }
 
@@ skipping 124 matching lines @@
     CACHE_HISTOGRAM_TIME("EraseValid.ValidFor", -stale.expired_by);
   }
 }
 
 void HostCache::RecordEraseAll(EraseReason reason, base::TimeTicks now) {
   for (const auto& it : entries_)
     RecordErase(reason, now, it.second);
 }
 
 }  // namespace net