Add 'base::Time::Max()' to explicitly refer to the end of time.

base/time.cc

Index: base/time.cc
diff --git a/base/time.cc b/base/time.cc
index f04ebbcbdd4e01dac23f567e81f5dff21916e947..7055311e80e7d53df843b61dd63a67b816a74faa 100644
--- a/base/time.cc
+++ b/base/time.cc
@@ -9,6 +9,8 @@
 #include <float.h>
 #endif
 
+#include <limits>
+
 #include "base/sys_string_conversions.h"
 #include "base/third_party/nspr/prtime.h"
 
@@ -64,6 +66,11 @@ int64 TimeDelta::InMicroseconds() const {
 // Time -----------------------------------------------------------------------
 
 // static
+Time Time::Max() {
+  return Time(std::numeric_limits<int64>::max());
+}
+
+// static
 Time Time::FromTimeT(time_t tt) {
   if (tt == 0)
     return Time();  // Preserve 0 so we can tell it doesn't exist.