Update documentation of Performance.timing/navigation

Source/core/timing/Performance.idl

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 35 matching lines @@
     [MeasureAs=UnprefixedPerformanceTimeline] PerformanceEntryList getEntriesByName(DOMString name, optional DOMString entryType = null);
 
     // Resource Timing
     // https://w3c.github.io/resource-timing/#extensions-performance-interface
     // TODO(philipj): Unprefix these APIs.
     [MeasureAs=PrefixedPerformanceClearResourceTimings] void webkitClearResourceTimings();
     [MeasureAs=PrefixedPerformanceSetResourceTimingBufferSize] void webkitSetResourceTimingBufferSize(unsigned long maxSize);
     attribute EventHandler onwebkitresourcetimingbufferfull;
 
     // Navigation Timing
-    // http://www.w3.org/TR/navigation-timing/#sec-window.performance-attribute
-    // TODO(philipj): The Navigation Timing Rec. defines the (not partial)
-    // Performance interface, while https://w3c.github.io/navigation-timing/ has
-    // changed the interface in an incompatible way:
-    // https://github.com/w3c/navigation-timing/issues/22
-    [Measure] readonly attribute PerformanceTiming timing;
-    [Measure] readonly attribute PerformanceNavigation navigation;
+    // https://w3c.github.io/navigation-timing/#extensions-to-the-performance-interface
+    [SameObject, Measure] readonly attribute PerformanceTiming timing;
+    [SameObject, Measure] readonly attribute PerformanceNavigation navigation;
 
     // User Timing
     // https://w3c.github.io/user-timing/#extensions-performance-interface
     [MeasureAs=UnprefixedUserTiming, RaisesException] void mark(DOMString markName);
     [MeasureAs=UnprefixedUserTiming] void clearMarks(optional DOMString markName = null);
 
     [MeasureAs=UnprefixedUserTiming, RaisesException] void measure(DOMString measureName, optional DOMString startMark = null, optional DOMString endMark = null);
     [MeasureAs=UnprefixedUserTiming] void clearMeasures(optional DOMString measureName = null);
 
     // Frame Timing
     // https://w3c.github.io/frame-timing/#extensions-performance-interface
     [RuntimeEnabled=FrameTimingSupport, MeasureAs=PerformanceFrameTiming] void clearFrameTimings();
     [RuntimeEnabled=FrameTimingSupport, MeasureAs=PerformanceFrameTiming] void setFrameTimingBufferSize(unsigned long maxSize);
     [RuntimeEnabled=FrameTimingSupport] attribute EventHandler onframetimingbufferfull;
 
     // TODO(philipj): There is no spec for the Memory Info API, see blink-dev:
     // https://groups.google.com/a/chromium.org/d/msg/blink-dev/g5YRCGpC9vs/b4OJz71NmPwJ
     [Measure] readonly attribute MemoryInfo memory;
 };