Fixing GraphicsContext state checks to support oilpan

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 80 matching lines @@
     return adoptRefWillBeRefCountedGarbageCollected(new HTMLCanvasElement(document));
 }
 
 HTMLCanvasElement::~HTMLCanvasElement()
 {
     v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(-m_externallyAllocatedMemory);
 #if !ENABLE(OILPAN)
     HashSet<RawPtr<CanvasObserver> >::iterator end = m_observers.end();
     for (HashSet<RawPtr<CanvasObserver> >::iterator it = m_observers.begin(); it != end; ++it)
         (*it)->canvasDestroyed(this);
-    m_context.clear(); // Ensure this goes away before the ImageBuffer.
+    // Ensure these go away before the ImageBuffer.
+    m_contextStateSaver.clear();

[zerny-chromium, 2014/05/28 06:17:26]

This should be outside the #if !ENABLE(OILPAN) since it is an own ptr in both
builds.

A quick question regarding the comment above: what issue can arise if the
ImageBuffer is torn down before the CanvasRenderingContext?

In the oilpan build the HTMLCanvasElement (and via an OwnPtr ImageBuffer) can be
torn down in the same GC round as the CanvasRenderingContext which means their
finalization order is not known.

+    m_context.clear();
 #endif
 }
 
 void HTMLCanvasElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (name == widthAttr || name == heightAttr)
         reset();
     HTMLElement::parseAttribute(name, value);
 }
 
@@ skipping 396 matching lines @@
     m_imageBuffer->context()->setImageInterpolationQuality(CanvasDefaultInterpolationQuality);
     // Enabling MSAA overrides a request to disable antialiasing. This is true regardless of whether the
     // rendering mode is accelerated or not. For consistency, we don't want to apply AA in accelerated
     // canvases but not in unaccelerated canvases.
     if (!msaaSampleCount && document().settings() && !document().settings()->antialiased2dCanvasEnabled())
         m_imageBuffer->context()->setShouldAntialias(false);
     // GraphicsContext's defaults don't always agree with the 2d canvas spec.
     // See CanvasRenderingContext2D::State::State() for more information.
     m_imageBuffer->context()->setMiterLimit(10);
     m_imageBuffer->context()->setStrokeThickness(1);
+#if !ASSERT_DISABLED
+    m_imageBuffer->context()->disableDestructionChecks(); // 2D canvas is allowed to leave context in an unfinalized state.
+#endif
     m_contextStateSaver = adoptPtr(new GraphicsContextStateSaver(*m_imageBuffer->context()));
 
     if (m_context)
         setNeedsCompositingUpdate();
 }
 
 void HTMLCanvasElement::notifySurfaceInvalid()
 {
     if (m_context && m_context->is2d()) {
         CanvasRenderingContext2D* context2d = toCanvasRenderingContext2D(m_context.get());
@@ skipping 167 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }