Allow constexpr variables of TimeDelta type.

base/time/time_unittest.cc

Index: base/time/time_unittest.cc
diff --git a/base/time/time_unittest.cc b/base/time/time_unittest.cc
index 8a6a7f517728335660c180788cadcd158abcb78a..5b215fbf94525af222d082ebb3b209539e0db2d0 100644
--- a/base/time/time_unittest.cc
+++ b/base/time/time_unittest.cc
@@ -723,16 +723,21 @@ TEST(TimeTicks, SnappedToNextTickOverflow) {
 }
 
 TEST(TimeDelta, FromAndIn) {
-  EXPECT_TRUE(TimeDelta::FromDays(2) == TimeDelta::FromHours(48));
-  EXPECT_TRUE(TimeDelta::FromHours(3) == TimeDelta::FromMinutes(180));
-  EXPECT_TRUE(TimeDelta::FromMinutes(2) == TimeDelta::FromSeconds(120));
-  EXPECT_TRUE(TimeDelta::FromSeconds(2) == TimeDelta::FromMilliseconds(2000));
-  EXPECT_TRUE(TimeDelta::FromMilliseconds(2) ==
-              TimeDelta::FromMicroseconds(2000));
-  EXPECT_TRUE(TimeDelta::FromSecondsD(2.3) ==
-              TimeDelta::FromMilliseconds(2300));
-  EXPECT_TRUE(TimeDelta::FromMillisecondsD(2.5) ==
-              TimeDelta::FromMicroseconds(2500));
+  // static_assert also checks that the contained expression is a constant
+  // expression, meaning all its components are suitable for initializing global
+  // variables.
+  static_assert(TimeDelta::FromDays(2) == TimeDelta::FromHours(48), "");
+  static_assert(TimeDelta::FromHours(3) == TimeDelta::FromMinutes(180), "");
+  static_assert(TimeDelta::FromMinutes(2) == TimeDelta::FromSeconds(120), "");
+  static_assert(TimeDelta::FromSeconds(2) == TimeDelta::FromMilliseconds(2000),
+                "");
+  static_assert(
+      TimeDelta::FromMilliseconds(2) == TimeDelta::FromMicroseconds(2000), "");
+  static_assert(
+      TimeDelta::FromSecondsD(2.3) == TimeDelta::FromMilliseconds(2300), "");
+  static_assert(
+      TimeDelta::FromMillisecondsD(2.5) == TimeDelta::FromMicroseconds(2500),
+      "");
   EXPECT_EQ(13, TimeDelta::FromDays(13).InDays());
   EXPECT_EQ(13, TimeDelta::FromHours(13).InHours());
   EXPECT_EQ(13, TimeDelta::FromMinutes(13).InMinutes());
@@ -855,18 +860,26 @@ TEST(TimeDelta, MaxConversions) {
 
   int64_t max_int = std::numeric_limits<int64_t>::max();
 
+  t = TimeDelta::FromSeconds(max_int / Time::kMicrosecondsPerSecond);
+  EXPECT_FALSE(t.is_max());
   t = TimeDelta::FromSeconds(max_int / Time::kMicrosecondsPerSecond + 1);
   EXPECT_TRUE(t.is_max());
 
+  t = TimeDelta::FromMilliseconds(max_int / Time::kMillisecondsPerSecond);
+  EXPECT_FALSE(t.is_max());
   t = TimeDelta::FromMilliseconds(max_int / Time::kMillisecondsPerSecond + 1);
   EXPECT_TRUE(t.is_max());
 
   t = TimeDelta::FromMicroseconds(max_int);
   EXPECT_TRUE(t.is_max());
 
+  t = TimeDelta::FromSeconds(-max_int / Time::kMicrosecondsPerSecond);
+  EXPECT_FALSE(IsMin(t));
   t = TimeDelta::FromSeconds(-max_int / Time::kMicrosecondsPerSecond - 1);
   EXPECT_TRUE(IsMin(t));
 
+  t = TimeDelta::FromMilliseconds(-max_int / Time::kMillisecondsPerSecond);
+  EXPECT_FALSE(IsMin(t));
   t = TimeDelta::FromMilliseconds(-max_int / Time::kMillisecondsPerSecond - 1);
   EXPECT_TRUE(IsMin(t));
 
@@ -880,21 +893,35 @@ TEST(TimeDelta, MaxConversions) {
   EXPECT_TRUE(t.is_max());
 
   double max_d = max_int;
+  // Converting max_int to double changes its value.
+  EXPECT_EQ(pow(2.0, 63), max_d);
 
-  t = TimeDelta::FromSecondsD(max_d / Time::kMicrosecondsPerSecond + 1);
+  t = TimeDelta::FromSecondsD(max_d / Time::kMicrosecondsPerSecond);
   EXPECT_TRUE(t.is_max());
+  t = TimeDelta::FromSecondsD(
+      nexttoward(max_d / Time::kMicrosecondsPerSecond, 0));
+  EXPECT_FALSE(t.is_max());
 
   t = TimeDelta::FromMillisecondsD(std::numeric_limits<double>::infinity());
   EXPECT_TRUE(t.is_max());
 
-  t = TimeDelta::FromMillisecondsD(max_d / Time::kMillisecondsPerSecond * 2);
-  EXPECT_TRUE(t.is_max());
+  t = TimeDelta::FromMillisecondsD(max_d / Time::kMillisecondsPerSecond);
+  EXPECT_TRUE(t.is_max()) << t;
+  t = TimeDelta::FromMillisecondsD(
+      nexttoward(max_d / Time::kMillisecondsPerSecond, 0));
+  EXPECT_FALSE(t.is_max());
 
-  t = TimeDelta::FromSecondsD(-max_d / Time::kMicrosecondsPerSecond - 1);
+  t = TimeDelta::FromSecondsD(-max_d / Time::kMicrosecondsPerSecond);
   EXPECT_TRUE(IsMin(t));
+  t = TimeDelta::FromSecondsD(
+      nexttoward(-max_d / Time::kMicrosecondsPerSecond, 0));
+  EXPECT_FALSE(IsMin(t));
 
-  t = TimeDelta::FromMillisecondsD(-max_d / Time::kMillisecondsPerSecond * 2);
-  EXPECT_TRUE(IsMin(t));
+  t = TimeDelta::FromMillisecondsD(-max_d / Time::kMillisecondsPerSecond);
+  EXPECT_TRUE(IsMin(t)) << t;
+  t = TimeDelta::FromMillisecondsD(
+      nexttoward(-max_d / Time::kMillisecondsPerSecond, 0));
+  EXPECT_FALSE(IsMin(t));
 }
 
 TEST(TimeDelta, NumericOperators) {