[base] Implement CPU time on Windows.

src/base/platform/time.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_BASE_PLATFORM_TIME_H_
 #define V8_BASE_PLATFORM_TIME_H_
 
 #include <ctime>
 #include <iosfwd>
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/base/macros.h"
 #include "src/base/safe_math.h"
+#if V8_OS_WIN
+#include "src/base/win32-headers.h"
+#endif
 
 // Forward declarations.
 extern "C" {
 struct _FILETIME;
 struct mach_timespec;
 struct timespec;
 struct timeval;
 }
 
 namespace v8 {
@@ skipping 348 matching lines @@
 
 // Represents a clock, specific to a particular thread, than runs only while the
 // thread is running.
 class ThreadTicks final : public time_internal::TimeBase<ThreadTicks> {
  public:
   ThreadTicks() : TimeBase(0) {}
 
   // Returns true if ThreadTicks::Now() is supported on this system.
   static bool IsSupported();
 
+  // Waits until the initialization is completed. Needs to be guarded with a
+  // call to IsSupported().
+  static void WaitUntilInitialized() {
+#if V8_OS_WIN
+    WaitUntilInitializedWin();
+#endif
+  }
+
   // Returns thread-specific CPU-time on systems that support this feature.
   // Needs to be guarded with a call to IsSupported(). Use this timer
   // to (approximately) measure how much time the calling thread spent doing
   // actual work vs. being de-scheduled. May return bogus results if the thread
   // migrates to another CPU between two calls. Returns an empty ThreadTicks
-  // object until the initialization is completed.
+  // object until the initialization is completed. If a clock reading is
+  // absolutely needed, call WaitUntilInitialized() before this method.
   static ThreadTicks Now();
 
+#if V8_OS_WIN
+  // Similar to Now() above except this returns thread-specific CPU time for an
+  // arbitrary thread. All comments for Now() method above apply apply to this
+  // method as well.
+  static ThreadTicks GetForThread(const HANDLE& thread_handle);
+#endif
+
  private:
-  // This is for internal use and testing. Ticks are in microseconds.
+  // Please use Now() or GetForThread() to create a new object. This is for
+  // internal use and testing. Ticks are in microseconds.
   explicit ThreadTicks(int64_t ticks) : TimeBase(ticks) {}
+
+#if V8_OS_WIN
+  // Returns the frequency of the TSC in ticks per second, or 0 if it hasn't
+  // been measured yet. Needs to be guarded with a call to IsSupported().
+  static double TSCTicksPerSecond();
+  static bool IsSupportedWin();
+  static void WaitUntilInitializedWin();
+#endif
 };
 
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_PLATFORM_TIME_H_