Use a monotonic clock (TimeTicks) to report network times to WebCore.

content/common/inter_process_time_ticks_converter.cc

+// Copyright (c) 2011 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 "content/common/inter_process_time_ticks_converter.h"
+
+#include "base/logging.h"
+
+namespace content {
+
+InterProcessTimeTicksConverter::InterProcessTimeTicksConverter(
+    const LocalTimeTicks& local_lower_bound,
+    const LocalTimeTicks& local_upper_bound,
+    const RemoteTimeTicks& remote_lower_bound,
+    const RemoteTimeTicks& remote_upper_bound)
+    : remote_lower_bound_(remote_lower_bound.value_),
+      remote_upper_bound_(remote_upper_bound.value_) {
+  int64 target_range = local_upper_bound.value_ - local_lower_bound.value_;
+  int64 source_range = remote_upper_bound.value_ - remote_lower_bound.value_;
+  if (source_range <= target_range) {
+    // We fit!  Just shift the midpoints to match.
+    numerator_ = 1;
+    denominator_ = 1;
+    offset_ = ((local_upper_bound.value_ + local_lower_bound.value_) -
+               (remote_upper_bound.value_ + remote_lower_bound.value_)) / 2;
+    return;
+  }
+  // Set up scaling factors, and then deduce shift.
+  numerator_ = target_range;
+  denominator_ = source_range;
+  // Find out what we need to shift by to make this really work.
+  offset_ = local_lower_bound.value_ - Convert(remote_lower_bound.value_);
+  DCHECK_GE(local_upper_bound.value_, Convert(remote_upper_bound.value_));
+}
+
+LocalTimeTicks InterProcessTimeTicksConverter::ToLocalTimeTicks(
+    const RemoteTimeTicks& remote_ms) {
+  DCHECK_LE(remote_lower_bound_, remote_ms.value_);
+  DCHECK_GE(remote_upper_bound_, remote_ms.value_);
+  RemoteTimeDelta remote_delta = remote_ms - remote_lower_bound_;
+  return LocalTimeTicks(remote_lower_bound_ + offset_ +
+                        ToLocalTimeDelta(remote_delta).value_);
+}
+
+LocalTimeDelta InterProcessTimeTicksConverter::ToLocalTimeDelta(
+    const RemoteTimeDelta& remote_delta) {
+  DCHECK_GE(remote_upper_bound_, remote_lower_bound_ + remote_delta.value_);
+  return LocalTimeDelta(Convert(remote_delta.value_));
+}
+
+int64 InterProcessTimeTicksConverter::Convert(int64 value) {
+  if (value <= 0) {
+    return value;
+  }
+  return numerator_ * value / denominator_;
+}
+
+}  // namespace content