Tried using CrossThreadPersistent for workerDebuggerAgents

Source/core/inspector/InjectedScriptHost.idl

 /*
  * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
  * Copyright (C) 2010 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
@@ skipping 13 matching lines @@
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
+    WillBeGarbageCollected,
     NoInterfaceObject
 ] interface InjectedScriptHost {
     void clearConsoleMessages();
 
     [Custom] void inspect(any objectId, any hints);
     [Custom] any inspectedObject(long num);
     [Custom] any internalConstructorName(any obj);
     [Custom] boolean isHTMLAllCollection(any obj);
     [Custom] DOMString type(any obj);
     [Custom] any functionDetails(any obj);
     [Custom] any[] getInternalProperties(any obj);
     [Custom] EventListener[] getEventListeners(EventTarget target);
     [Custom] any evaluate(DOMString text);
     [Custom] void debugFunction(any fn);
     [Custom] void undebugFunction(any fn);
     [Custom] void monitorFunction(any fn);
     [Custom] void unmonitorFunction(any fn);
     [Custom] any suppressWarningsAndCall(any receiver, any fn, any param1, any param2);
 
     // Only declarative scope (local, with and catch) is accepted. Returns undefined.
     [Custom] any setFunctionVariableValue(any functionObject, long scopeIndex, DOMString variableName, any newValue);
 };