Surfaces system timestamp in the blink platform interface.

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 25faab4b5b5a80c78133361e56a334c2725175dd..886cfdc3ed1487a8ec984c3eac57525c9f299b8d 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -1049,6 +1049,11 @@ double BlinkPlatformImpl::monotonicallyIncreasingTime() {
       static_cast<double>(base::Time::kMicrosecondsPerSecond);
 }
 
+double BlinkPlatformImpl::systemTraceTime() {
+  return base::TimeTicks::NowFromSystemTraceTime().ToInternalValue() /
+      static_cast<double>(base::Time::kMicrosecondsPerSecond);
+}
+
 void BlinkPlatformImpl::cryptographicallyRandomValues(
     unsigned char* buffer, size_t length) {
   base::RandBytes(buffer, length);