time: Add a static TimeTicks method that returns the underlying clock

base/time/time.h

Index: base/time/time.h
diff --git a/base/time/time.h b/base/time/time.h
index 066d910833d2091e60a97870daf0aa7c800dc630..1989dbf8f27758e0643a3732859bcb62aca672c2 100644
--- a/base/time/time.h
+++ b/base/time/time.h
@@ -642,6 +642,15 @@ BASE_EXPORT std::ostream& operator<<(std::ostream& os, Time time);
 // Represents monotonically non-decreasing clock time.
 class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
  public:
+  // The underlying clock used to generate new TimeTicks.
+  enum class Clock {
+    LINUX_CLOCK_MONOTONIC,
+    IOS_CF_ABSOLUTE_TIME_MINUS_KERN_BOOTTIME,
+    MAC_MACH_ABSOLUTE_TIME,
+    WIN_QPC,
+    WIN_ROLLOVER_PROTECTED_TIME_GET_TIME
+  };
+
   TimeTicks() : TimeBase(0) {
   }
 
@@ -680,6 +689,11 @@ class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
   TimeTicks SnappedToNextTick(TimeTicks tick_phase,
                               TimeDelta tick_interval) const;
 
+  // Returns an enum indicating the underlying clock being used to generate
+  // TimeTicks timestamps. This function should only be used for debugging and
+  // logging purposes.
+  static Clock GetClock();
+
 #if defined(OS_WIN)
  protected:
   typedef DWORD (*TickFunctionType)(void);