Allow BackoffEntry to be serialized and deserialized.

net/base/backoff_entry_serializer.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 "net/base/backoff_entry_serializer.h"
+
+#include "base/strings/string_number_conversions.h"
+#include "base/time/tick_clock.h"
+#include "base/values.h"
+#include "net/base/backoff_entry.h"
+
+namespace {
+// Increment this number if we change serialization format, so we don't
+// misinterpret old serialized values loaded from disk etc.
+const int kSerializationFormatVersion = 1;
+}  // namespace
+
+namespace net {
+
+scoped_ptr<base::Value> BackoffEntrySerializer::SerializeToValue(
+    const BackoffEntry& entry, base::Time time_now) {
+  scoped_ptr<base::ListValue> serialized(new base::ListValue());
+  serialized->AppendInteger(kSerializationFormatVersion);
+
+  serialized->AppendInteger(entry.failure_count());
+
+  // Can't use entry.GetTimeUntilRelease as it doesn't allow negative deltas.
+  base::TimeDelta backoff_duration =
+      entry.GetReleaseTime() - entry.tick_clock()->NowTicks();
+  // Redundantly stores both the remaining time delta and the absolute time.
+  // The delta is used to work around some cases where wall clock time changes.
+  serialized->AppendDouble(backoff_duration.InSecondsF());
+  base::Time absolute_release_time = backoff_duration + time_now;
+  serialized->AppendString(
+      base::Int64ToString(absolute_release_time.ToInternalValue()));
+
+  return serialized.Pass();
+}
+
+scoped_ptr<BackoffEntry> BackoffEntrySerializer::DeserializeFromValue(
+    const base::Value& serialized, const BackoffEntry::Policy* policy,
+    base::TickClock* tick_clock, base::Time time_now) {
+  const base::ListValue* serialized_list = nullptr;
+  if (!serialized.GetAsList(&serialized_list))
+    return nullptr;
+  if (serialized_list->GetSize() != 4)
+    return nullptr;
+  int version_number;
+  if (!serialized_list->GetInteger(0, &version_number) ||
+      version_number != kSerializationFormatVersion) {
+    return nullptr;
+  }
+
+  int failure_count;
+  if (!serialized_list->GetInteger(1, &failure_count) || failure_count < 0)
+    return nullptr;
+  double original_backoff_duration_double;
+  if (!serialized_list->GetDouble(2, &original_backoff_duration_double))
+    return nullptr;
+  std::string absolute_release_time_string;
+  if (!serialized_list->GetString(3, &absolute_release_time_string))
+    return nullptr;
+  int64 absolute_release_time_us;
+  if (!base::StringToInt64(absolute_release_time_string,
+                           &absolute_release_time_us)
+      || absolute_release_time_us < 0) {

[mmenke, 2015/05/06 20:48:44]

|| should go on the previous line, I believe.  You are running "git cl format
net", right?  Should get a presubmit error if you don't.  Fine if this is the
code that results in.

[johnme, 2015/05/07 12:16:00]

Done (`git cl format net` allows both, and the style guide[1] just says to be
consistent; but having them at the end of the line is indeed much more common in
net/).

[1]:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Boolean_Expre...

+    return nullptr;
+  }
+
+  scoped_ptr<BackoffEntry> entry(new BackoffEntry(policy, tick_clock));
+
+  for (int n = 0; n < failure_count; n++)
+    entry->InformOfRequest(false);
+
+  base::TimeDelta original_backoff_duration =
+      base::TimeDelta::FromSecondsD(original_backoff_duration_double);
+  base::Time absolute_release_time =
+      base::Time::FromInternalValue(absolute_release_time_us);
+  base::TimeDelta backoff_duration = absolute_release_time - time_now;
+  // In cases where the system wall clock is rewound, use the redundant
+  // original_backoff_duration to ensure the backoff duration isn't longer
+  // than it was before serializing (note that it's not possible to protect
+  // against the clock being wound forward).
+  if (backoff_duration > original_backoff_duration)
+    backoff_duration = original_backoff_duration;
+  entry->SetCustomReleaseTime(
+      entry->BackoffDurationToReleaseTime(backoff_duration));
+
+  return entry;
+}
+
+}  // namespace net