Fixing GraphicsContext state checks to support oilpan

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 88f05be55e4d05be983401dbf35925bde4185a00..466788272dc19f3fde9044ed0db6c295d71232ac 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -97,7 +97,9 @@ HTMLCanvasElement::~HTMLCanvasElement()
         (*it)->canvasDestroyed(this);
 
 #if !ENABLE(OILPAN)
-    m_context.clear(); // Ensure this goes away before the ImageBuffer.
+    // Ensure these go away before the ImageBuffer.
+    m_contextStateSaver.clear();
+    m_context.clear();
 #endif
 }
 
@@ -514,6 +516,9 @@ void HTMLCanvasElement::createImageBufferInternal()
     // 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.

[f(malita), 2014/05/27 20:28:22]

If we have exclusive control of the initialization path, I would prefer this to
be a GraphicsContext constructor flag. But it's unclear whether that's feasible.

[Justin Novosad, 2014/05/27 22:25:25]

Right no ImageBuffer is not explicitly aware that it is owned by a 2D canvas,
but we could still have a construction flag relayed through ImageBuffer.

+#endif
     m_contextStateSaver = adoptPtr(new GraphicsContextStateSaver(*m_imageBuffer->context()));
 
     if (m_context)