Also copy the fallback code.

runtime/bin/utils_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include <errno.h>  // NOLINT
 #include <time.h>  // NOLINT
 
@@ skipping 150 matching lines @@
     unicode_argc = argc;
   }
   for (int i = 0; i < unicode_argc; i++) {
     wchar_t* arg = unicode_argv[i];
     argv[i] = StringUtilsWin::WideToUtf8(arg);
   }
   LocalFree(unicode_argv);
   return true;
 }
 
+static int64_t GetCurrentTimeMicros() {
+  static const int64_t kTimeEpoc = 116444736000000000LL;
+  static const int64_t kTimeScaler = 10;  // 100 ns to us.
+
+  // Although win32 uses 64-bit integers for representing timestamps,
+  // these are packed into a FILETIME structure. The FILETIME
+  // structure is just a struct representing a 64-bit integer. The
+  // TimeStamp union allows access to both a FILETIME and an integer
+  // representation of the timestamp. The Windows timestamp is in
+  // 100-nanosecond intervals since January 1, 1601.
+  union TimeStamp {
+    FILETIME ft_;
+    int64_t t_;
+  };
+  TimeStamp time;
+  GetSystemTimeAsFileTime(&time.ft_);
+  return (time.t_ - kTimeEpoc) / kTimeScaler;
+}
+
 int64_t TimerUtils::GetCurrentMonotonicMillis() {
   return GetCurrentMonotonicMicros() / 1000;
 }
 
 static int64_t qpc_ticks_per_second = 0;
 
 int64_t TimerUtils::GetCurrentMonotonicMicros() {
   if (qpc_ticks_per_second == 0) {
     // QueryPerformanceCounter not supported, fallback.
     return GetCurrentTimeMicros();
@@ skipping 11 matching lines @@
 }
 
 void TimerUtils::Sleep(int64_t millis) {
   ::Sleep(millis);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)