Determine if OffscreenCanvas is paintable in different rendering contexts

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.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/offscreencanvas2d/OffscreenCanvasRenderingContext2D.h"
 
 #include "bindings/modules/v8/OffscreenCanvasRenderingContext2DOrWebGLRenderingContextOrWebGL2RenderingContext.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/Settings.h"
 #include "core/workers/WorkerGlobalScope.h"
@@ skipping 177 matching lines @@
         ASSERT(static_cast<size_t>(skCanvas->getSaveCount()) == m_stateStack.size());
     }
 #endif
 }
 
 bool OffscreenCanvasRenderingContext2D::isContextLost() const
 {
     return false;
 }
 
+bool OffscreenCanvasRenderingContext2D::isPaintable() const
+{
+    return this->imageBuffer();
 }
+}