Expose worklet on Window through attribute renderWorklet.

third_party/WebKit/Source/modules/worklet/WorkletGlobalScope.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/worklet/WorkletGlobalScope.h"
 
 #include "bindings/core/v8/WorkerOrWorkletScriptController.h"
 
 namespace blink {
 
 // static
 PassRefPtrWillBeRawPtr<WorkletGlobalScope> WorkletGlobalScope::create(const KURL& url, const String& userAgent, v8::Isolate* isolate)
 {
-    return adoptRefWillBeNoop(new WorkletGlobalScope(url, userAgent, isolate));
+    RefPtrWillBeRawPtr<WorkletGlobalScope> workletGlobalScope = adoptRefWillBeNoop(new WorkletGlobalScope(url, userAgent, isolate));
+    workletGlobalScope->script()->initializeContextIfNeeded();

[ikilpatrick, 2016/01/14 19:31:57]

This was added here as within:
V8DOMWrapper::associateObjectWithWrapper (inside initializeContextIfNeeded())

there is an assert to check that the GlobalScope is adopted by something.

+    return workletGlobalScope.release();
 }
 
 WorkletGlobalScope::WorkletGlobalScope(const KURL& url, const String& userAgent, v8::Isolate* isolate)
     : m_script(WorkerOrWorkletScriptController::create(this, isolate))
 {
-    m_script->initializeContextIfNeeded();
 }
 
 WorkletGlobalScope::~WorkletGlobalScope()
 {
 }
 
 v8::Local<v8::Object> WorkletGlobalScope::wrap(v8::Isolate*, v8::Local<v8::Object> creationContext)
 {
     // WorkletGlobalScope must never be wrapped with wrap method. The global
     // object of ECMAScript environment is used as the wrapper.
@@ skipping 32 matching lines @@
 }
 
 DEFINE_TRACE(WorkletGlobalScope)
 {
     visitor->trace(m_script);
     ExecutionContext::trace(visitor);
     SecurityContext::trace(visitor);
 }
 
 } // namespace blink