Reland "Linux perf tool support update + refactoring." (r22146, attempt #5)

src/base/platform/time.h

Index: src/base/platform/time.h
diff --git a/src/base/platform/time.h b/src/base/platform/time.h
index aed03b10eba2ce086ad5a33f39214b2c0d97a748..b348236ff1ccc59323e6eba66b1b4a91e20291ad 100644
--- a/src/base/platform/time.h
+++ b/src/base/platform/time.h
@@ -315,6 +315,13 @@ class TimeTicks V8_FINAL {
   // Returns true if the high-resolution clock is working on this system.
   static bool IsHighResolutionClockWorking();
 
+  // Returns Linux kernel timestamp for generating profiler events. This method
+  // returns null TimeTicks if the kernel cannot provide the timestamps (e.g.,
+  // on non-Linux OS or if the kernel module for timestamps is not loaded).
+
+  static TimeTicks KernelTimestampNow();
+  static bool KernelTimestampAvailable();
+
   // Returns true if this object has not been initialized.
   bool IsNull() const { return ticks_ == 0; }