Add Javascript time methods to base::Time.

base/time.h

 // 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.
 
 // Time represents an absolute point in time, internally represented as
 // microseconds (s/1,000,000) since a platform-dependent epoch.  Each
 // platform's epoch, along with other system-dependent clock interface
 // routines, is defined in time_PLATFORM.cc.
 //
 // TimeDelta represents a duration of time, internally represented in
@@ skipping 248 matching lines @@
   time_t ToTimeT() const;
 
   // Converts time to/from a double which is the number of seconds since epoch
   // (Jan 1, 1970).  Webkit uses this format to represent time.
   // Because WebKit initializes double time value to 0 to indicate "not
   // initialized", we map it to empty Time object that also means "not
   // initialized".
   static Time FromDoubleT(double dt);
   double ToDoubleT() const;
 
+  // Converts to/from the Javascript convention for times, a number of
+  // milliseconds since the epoch:
+  // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
+  static Time FromJsTime(double ms_since_epoch);
+  double ToJsTime() const;
+
 #if defined(OS_POSIX)
   struct timeval ToTimeVal() const;
 #endif
 
 #if defined(OS_WIN)
   static Time FromFileTime(FILETIME ft);
   FILETIME ToFileTime() const;
 
   // The minimum time of a low resolution timer.  This is basically a windows
   // constant of ~15.6ms.  While it does vary on some older OS versions, we'll
@@ skipping 303 matching lines @@
 #endif
 };
 
 inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
   return TimeTicks(t.ticks_ + delta_);
 }
 
 }  // namespace base
 
 #endif  // BASE_TIME_H_