Add explicit TimeDelta constexpr copy constructor.

base/time/time_unittest.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 "base/time/time.h"
 
 #include <stdint.h>
 #include <time.h>
 #include <limits>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/platform_thread.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 namespace {
 
+// For TimeDelta::ConstexprInitialization
+enum { kExpectedDeltaInMilliseconds = 10 };

[miu, 2016/08/11 21:48:56]

Is it necessary for this to be an enum to trigger the compiler error? Otherwise,
nit: Please make this constexpr int64_t kExpected... = 10;

[liberato (no reviews please), 2016/08/11 22:10:35]

it's not necessary.

originally, i had it as constexpr.  it seemed a bit like a red-herring, given
the subject of the test.  i'll switch it back.

+constexpr TimeDelta kConstexprTimeDelta =
+    TimeDelta::FromMilliseconds(kExpectedDeltaInMilliseconds);
+
 TEST(TimeTestOutOfBounds, FromExplodedOutOfBoundsTime) {
   // FromUTCExploded must set time to Time(0) and failure, if the day is set to
   // 31 on a 28-30 day month. Test |exploded| returns Time(0) on 31st of
   // February and 31st of April. New implementation handles this.
 
   const struct DateTestData {
     Time::Exploded explode;
     bool is_valid;
   } kDateTestData[] = {
       // 31st of February
@@ skipping 1052 matching lines @@
 
   Time time_now = Time::Now();
   EXPECT_EQ(one_second, (time_now + one_second) - time_now);
   EXPECT_EQ(-one_second, (time_now - one_second) - time_now);
 
   TimeTicks ticks_now = TimeTicks::Now();
   EXPECT_EQ(-one_second, (ticks_now - one_second) - ticks_now);
   EXPECT_EQ(one_second, (ticks_now + one_second) - ticks_now);
 }
 
+TEST(TimeDelta, ConstexprInitialization) {

[miu, 2016/08/11 21:48:56]

Please put these changes in time_win_unittest.cc instead, since they're
addressing a Windows compiler-specific bug.

[liberato (no reviews please), 2016/08/11 22:10:35]

Done.

+  // Make sure that TimeDelta works around crbug.com/635974
+  EXPECT_EQ(kExpectedDeltaInMilliseconds, kConstexprTimeDelta.InMilliseconds());
+}
+
 TEST(TimeDeltaLogging, DCheckEqCompiles) {
   DCHECK_EQ(TimeDelta(), TimeDelta());
 }
 
 TEST(TimeDeltaLogging, EmptyIsZero) {
   TimeDelta zero;
   EXPECT_EQ("0s", AnyToString(zero));
 }
 
 TEST(TimeDeltaLogging, FiveHundredMs) {
@@ skipping 67 matching lines @@
 
 TEST(TimeTicksLogging, DoesNotMakeStreamBad) {
   std::ostringstream oss;
   oss << TimeTicks();
   EXPECT_TRUE(oss.good());
 }
 
 }  // namespace
 
 }  // namespace base