Fixing Time::Max()'s behavior with Time::ToTimeT() and friends.

base/time.h

Index: base/time.h
diff --git a/base/time.h b/base/time.h
index 4d9bf350c598c336ed8e2c81b8bf65dadbd9ed4d..ceed500f5640286f8ac06c4e5e1c58bdedd0f51f 100644
--- a/base/time.h
+++ b/base/time.h
@@ -45,6 +45,8 @@
 #include <windows.h>
 #endif
 
+#include <limits>
+
 namespace base {
 
 class Time;
@@ -246,6 +248,11 @@ class BASE_EXPORT Time {
     return us_ == 0;
   }
 
+  // Returns true if the time object is the maximum time.
+  bool is_max() const {
+    return us_ == std::numeric_limits<int64>::max();
+  }
+
   // Returns the time for epoch in Unix-like system (Jan 1, 1970).
   static Time UnixEpoch();