Use base/time/time_posix.cc on OS X and iOS.

base/BUILD.gn

 # Copyright (c) 2013 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.
 
 # HOW TO WRITE CONDITIONALS IN THIS FILE
 # ======================================
 #
 # In many other places, one would write a conditional that expresses all the
 # cases when a source file is used or unused, and then either add or subtract
 # it from the sources list in that case
@@ skipping 782 matching lines @@
     "time/clock.cc",
     "time/clock.h",
     "time/default_clock.cc",
     "time/default_clock.h",
     "time/default_tick_clock.cc",
     "time/default_tick_clock.h",
     "time/tick_clock.cc",
     "time/tick_clock.h",
     "time/time.cc",
     "time/time.h",
-    "time/time_mac.cc",
     "time/time_posix.cc",
     "time/time_win.cc",
     "timer/elapsed_timer.cc",
     "timer/elapsed_timer.h",
     "timer/hi_res_timer_manager.h",
     "timer/hi_res_timer_manager_posix.cc",
     "timer/hi_res_timer_manager_win.cc",
     "timer/mock_timer.cc",
     "timer/mock_timer.h",
     "timer/timer.cc",
@@ skipping 469 matching lines @@
       "mac/scoped_nsautorelease_pool.h",
       "mac/scoped_nsautorelease_pool.mm",
       "mac/scoped_nsobject.h",
       "mac/scoped_objc_class_swizzler.h",
       "mac/scoped_objc_class_swizzler.mm",
       "message_loop/message_pump_mac.h",
       "message_loop/message_pump_mac.mm",
       "process/memory_stubs.cc",
       "strings/sys_string_conversions_mac.mm",
       "threading/platform_thread_mac.mm",
-      "time/time_mac.cc",
     ]
 
     set_sources_assignment_filter(sources_assignment_filter)
   }
 
   if (!use_glib) {
     sources -= [
       "message_loop/message_pump_glib.cc",
       "message_loop/message_pump_glib.h",
     ]
@@ skipping 838 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }