[Cronet] Add metrics util to produce native date objects.

Bug: 879208
Change-Id: Ie57908edc90261202f7bfb82a9963403358df7b8
Reviewed-on: https://chromium-review.googlesource.com/c/1423351
Commit-Queue: Caleb Raitto <caraitto@chromium.org>
Reviewed-by: Misha Efimov <mef@chromium.org>
Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635741}

components/cronet/native/BUILD.gn

@@ -41,6 +41,7 @@ source_set("cronet_native_impl") {
     "//base",
     "//components/cronet:cronet_common",
     "//components/cronet:cronet_version_header",
+    "//components/cronet:metrics_util",
     "//components/grpc_support:grpc_support",
     "//net",
   ]
@@ -57,6 +58,8 @@ source_set("cronet_native_impl") {
     "engine.h",
     "io_buffer_with_cronet_buffer.cc",
     "io_buffer_with_cronet_buffer.h",
+    "native_metrics_util.cc",
+    "native_metrics_util.h",
     "runnables.cc",
     "runnables.h",
     "upload_data_sink.cc",
@@ -77,6 +80,7 @@ source_set("cronet_native_unittests") {
 
   deps = [
     ":cronet_native_impl",
+    "//base/test:test_support",
     "//components/cronet/native/test:cronet_native_testutil",
     "//net:test_support",
     "//testing/gtest",
@@ -85,6 +89,7 @@ source_set("cronet_native_unittests") {
   configs += [ ":cronet_native_include_config" ]
 
   sources = [
+    "native_metrics_util_test.cc",
     "runnables_unittest.cc",
 
     # Generated from cronet.idl.

components/cronet/native/native_metrics_util.cc

+// Copyright 2019 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 "components/cronet/native/native_metrics_util.h"
+
+#include "components/cronet/metrics_util.h"
+
+namespace cronet {
+
+namespace native_metrics_util {
+
+void ConvertTime(const base::TimeTicks& ticks,
+                 const base::TimeTicks& start_ticks,
+                 const base::Time& start_time,
+                 base::Optional<Cronet_DateTime>* out) {
+  Cronet_DateTime date_time;
+  date_time.value = metrics_util::ConvertTime(ticks, start_ticks, start_time);
+  if (date_time.value == metrics_util::kNullTime) {
+    (*out).reset();
+    return;
+  }
+  (*out).emplace(date_time);
+}
+
+}  // namespace native_metrics_util
+
+}  // namespace cronet

components/cronet/native/native_metrics_util.h

+// Copyright 2019 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_CRONET_NATIVE_NATIVE_METRICS_UTIL_H_
+#define COMPONENTS_CRONET_NATIVE_NATIVE_METRICS_UTIL_H_
+
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "components/cronet/native/generated/cronet.idl_impl_struct.h"
+
+namespace cronet {
+
+namespace native_metrics_util {
+
+// Converts timing metrics stored as TimeTicks into the format expected by the
+// native layer: a base::Optional<Cronet_DateTime> (which may be valueless if
+// either |ticks| or |start_ticks| is null) -- this is returned via |out|. An
+// out parameter is used because Cronet IDL structs like Cronet_DateTime aren't
+// assignable.
+//
+// By calculating time values using a base (|start_ticks|, |start_time|) pair,
+// time values are normalized. This allows time deltas between pairs of events
+// to be accurately computed, even if the system clock changed between those
+// events, as long as times for both events were calculated using the same
+// (|start_ticks|, |start_time|) pair.
+//
+// Args:
+//
+// ticks: The ticks value corresponding to the time of the event -- the returned
+//        time corresponds to this event.
+//
+// start_ticks: Ticks measurement at some base time -- the ticks equivalent of
+//              start_time. Should be smaller than ticks.
+//
+// start_time: Time measurement at some base time -- the time equivalent of
+//             start_ticks. Must not be null.
+//
+// out: The output of the function -- the existing pointee object is mutated to
+//      either hold the new Cronet_DateTime or nothing (if either |ticks| or
+//      |start_ticks| is null).
+void ConvertTime(const base::TimeTicks& ticks,
+                 const base::TimeTicks& start_ticks,
+                 const base::Time& start_time,
+                 base::Optional<Cronet_DateTime>* out);
+
+}  // namespace native_metrics_util
+
+}  // namespace cronet
+
+#endif  // COMPONENTS_CRONET_NATIVE_NATIVE_METRICS_UTIL_H_

components/cronet/native/native_metrics_util_test.cc

+// Copyright 2019 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 "components/cronet/native/native_metrics_util.h"
+
+#include "base/test/gtest_util.h"
+#include "base/time/time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cronet {
+
+namespace native_metrics_util {
+
+namespace {
+
+TEST(NativeMetricsUtilTest, ConvertsTimes) {
+  constexpr auto start_delta = base::TimeDelta::FromMilliseconds(20);
+  constexpr auto event_delta = base::TimeDelta::FromMilliseconds(30);
+
+  base::Optional<Cronet_DateTime> converted;
+  ConvertTime(base::TimeTicks::UnixEpoch() + event_delta,
+              base::TimeTicks::UnixEpoch() + start_delta,
+              base::Time::UnixEpoch() + start_delta, &converted);
+  ASSERT_TRUE(converted.has_value());
+  EXPECT_EQ(converted->value, 30);
+}
+
+TEST(NativeMetricsUtilTest, OverwritesOldOutParam) {
+  constexpr auto start_delta = base::TimeDelta::FromMilliseconds(20);
+  constexpr auto event_delta = base::TimeDelta::FromMilliseconds(30);
+
+  base::Optional<Cronet_DateTime> converted;
+  converted.emplace();
+  converted->value = 60;
+  ConvertTime(base::TimeTicks::UnixEpoch() + event_delta,
+              base::TimeTicks::UnixEpoch() + start_delta,
+              base::Time::UnixEpoch() + start_delta, &converted);
+  ASSERT_TRUE(converted.has_value());
+  EXPECT_EQ(converted->value, 30);
+}
+
+TEST(NativeMetricsUtilTest, NullTicks) {
+  constexpr auto start_delta = base::TimeDelta::FromMilliseconds(20);
+
+  base::Optional<Cronet_DateTime> converted;
+  ConvertTime(base::TimeTicks(), base::TimeTicks::UnixEpoch() + start_delta,
+              base::Time::UnixEpoch() + start_delta, &converted);
+  ASSERT_FALSE(converted.has_value());
+}
+
+TEST(NativeMetricsUtilTest, NullStartTicks) {
+  constexpr auto start_delta = base::TimeDelta::FromMilliseconds(20);
+  constexpr auto event_delta = base::TimeDelta::FromMilliseconds(30);
+
+  base::Optional<Cronet_DateTime> converted;
+  ConvertTime(base::TimeTicks::UnixEpoch() + event_delta, base::TimeTicks(),
+              base::Time::UnixEpoch() + start_delta, &converted);
+  ASSERT_FALSE(converted.has_value());
+}
+
+TEST(NativeMetricsUtilTest, NullStartTime) {
+  constexpr auto start_delta = base::TimeDelta::FromMilliseconds(20);
+  constexpr auto event_delta = base::TimeDelta::FromMilliseconds(30);
+
+  base::Optional<Cronet_DateTime> converted;
+  EXPECT_DCHECK_DEATH(ConvertTime(base::TimeTicks::UnixEpoch() + event_delta,
+                                  base::TimeTicks::UnixEpoch() + start_delta,
+                                  base::Time(), &converted));
+}
+
+}  // namespace
+
+}  // namespace native_metrics_util
+
+}  // namespace cronet