Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/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 18 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // https://w3c.github.io/hr-time/#the-performance-interface
 
 // TODO(philipj): This interface should be [Exposed=(Window,Worker)]. Doing that
 // would allow the WorkerPerformance interface to be merged into this.
 // TODO(philipj): None of the optional DOMString arguments in this interface
 // should have a default value.
 [
-  GarbageCollected
 ] interface Performance : EventTarget {
     DOMHighResTimeStamp now();
 
     // Performance Timeline
     // https://w3c.github.io/performance-timeline/#the-performance-interface
     // TODO(philipj): getEntries() should take an optional FilterOptions argument.
     [MeasureAs=UnprefixedPerformanceTimeline] PerformanceEntryList getEntries();
     [MeasureAs=UnprefixedPerformanceTimeline] PerformanceEntryList getEntriesByType(DOMString entryType);
     [MeasureAs=UnprefixedPerformanceTimeline] PerformanceEntryList getEntriesByName(DOMString name, optional DOMString entryType = null);
 
@@ skipping 24 matching lines @@
     // 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;
 };