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

third_party/WebKit/Source/core/timing/WorkerPerformance.idl

 /*
  * Copyright (C) 2013 Google 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * 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 merged into Performance.
 // TODO(philipj): None of the optional DOMString arguments in this interface
 // should have a default value.
 [
-    GarbageCollected,
     NoInterfaceObject
 ] interface WorkerPerformance : EventTarget {
     DOMHighResTimeStamp now();
 
     // Performance Timeline
     // https://w3c.github.io/performance-timeline/#the-performance-interface
     // TODO(philipj): getEntries() should take an optional FilterOptions argument.
     PerformanceEntryList getEntries();
     PerformanceEntryList getEntriesByType(DOMString entryType);
     PerformanceEntryList getEntriesByName(DOMString name, optional DOMString entryType = null);
 
     // Resource Timing
     // https://w3c.github.io/resource-timing/#extensions-performance-interface
     void clearResourceTimings();
     void setResourceTimingBufferSize(unsigned long maxSize);
     attribute EventHandler onresourcetimingbufferfull;
 
     // User Timing
     // https://w3c.github.io/user-timing/#extensions-performance-interface
     [RaisesException] void mark(DOMString markName);
     void clearMarks(optional DOMString markName = null);
 
     [RaisesException] void measure(DOMString measureName, optional DOMString startMark = null, optional DOMString endMark = null);
     void clearMeasures(optional DOMString measureName = null);
 
     // 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
     [RuntimeEnabled=MemoryInfoInWorkers] readonly attribute MemoryInfo memory;
 };