Fuchsia port of base/time, with some refactoring of POSIX time modules.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 49e16f5c0bdedc4956a7bf827fdf614834b8674c..d022a6cb4d1b7fd0ac5be73d0b9dd79bd8a4bdc9 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -924,9 +924,6 @@ component("base") {
     "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",
@@ -1345,6 +1342,7 @@ component("base") {
       "power_monitor/power_monitor_device_source_win.cc",
       "profiler/win32_stack_frame_unwinder.cc",
       "profiler/win32_stack_frame_unwinder.h",
+      "time/time_win.cc",
     ]
 
     sources -= [
@@ -1452,6 +1450,8 @@ component("base") {
     sources += [
       "mac/scoped_typeref.h",
       "power_monitor/power_monitor_device_source_mac.mm",
+      "time/time_conversion_posix.cc",
+      "time/time_mac.cc",
     ]
 
     libs = [
@@ -1597,12 +1597,30 @@ component("base") {
       "process/memory_stubs.cc",
       "strings/sys_string_conversions_mac.mm",
       "threading/platform_thread_mac.mm",
+      "time/time_conversion_posix.cc",
       "time/time_mac.cc",
     ]
 
     set_sources_assignment_filter(sources_assignment_filter)
   }
 
+  # Fuchsia.
+  if (is_fuchsia) {
+    sources += [
+      "time/time_conversion_posix.cc",
+      "time/time_exploded_posix.cc",
+      "time/time_fuchsia.cc",
+    ]
+  }
+
+  if (is_posix && !is_fuchsia && !is_mac && !is_ios) {
+    sources += [
+      "time/time_conversion_posix.cc",
+      "time/time_exploded_posix.cc",
+      "time/time_now_posix.cc",
+    ]
+  }
+
   if (is_posix && !is_mac && !is_ios && !is_android && !is_chromeos) {
     sources += [ "power_monitor/power_monitor_device_source_posix.cc" ]
   }