Sync core/timing/ interfaces with their specs, or lack thereof

Source/core/timing/PerformanceEntry.idl

Index: Source/core/timing/PerformanceEntry.idl
diff --git a/Source/core/timing/PerformanceEntry.idl b/Source/core/timing/PerformanceEntry.idl
index d5c2c9264c3092e4726c73ffa2fac88dcf2fc66e..b18ac79c240fdc70ca565380164700d777c25b29 100644
--- a/Source/core/timing/PerformanceEntry.idl
+++ b/Source/core/timing/PerformanceEntry.idl
@@ -29,13 +29,14 @@
  */
 
 // https://w3c.github.io/performance-timeline/#the-performanceentry-interface
+
 [
+    // TODO(philipj): Exposed=(Window,Worker)
     GarbageCollected,
 ] interface PerformanceEntry {
     readonly attribute DOMString name;
     readonly attribute DOMString entryType;
-    readonly attribute double startTime;
-    readonly attribute double duration;
-
+    readonly attribute DOMHighResTimeStamp startTime;
+    readonly attribute DOMHighResTimeStamp duration;
     serializer = {attribute};
 };