Lose/restore WebGL contexts if multisampling blackist status changes at runtime.

Source/core/html/canvas/WebGLRenderingContext.h

Index: Source/core/html/canvas/WebGLRenderingContext.h
diff --git a/Source/core/html/canvas/WebGLRenderingContext.h b/Source/core/html/canvas/WebGLRenderingContext.h
index 5314306c138a2396bd33bbcb2c1fd2d21cfa6209..654329188e2213a75a1367daa4ef5bf93824f7ba 100644
--- a/Source/core/html/canvas/WebGLRenderingContext.h
+++ b/Source/core/html/canvas/WebGLRenderingContext.h
@@ -29,6 +29,7 @@
 #include "core/dom/ActiveDOMObject.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/WebGLGetInfo.h"
+#include "core/page/Page.h"
 #include "core/platform/Timer.h"
 #include "core/platform/graphics/GraphicsContext3D.h"
 #include "core/platform/graphics/ImageBuffer.h"
@@ -294,7 +295,10 @@ public:
         RealLostContext,
 
         // Lost context provoked by WEBKIT_lose_context.
-        SyntheticLostContext
+        SyntheticLostContext,
+
+        // A synthetic lost context that should attempt to recover automatically
+        AutoRecoverSyntheticLostContext
     };
     void forceLostContext(LostContextMode);
     void forceRestoreContext();
@@ -331,7 +335,7 @@ public:
     friend class WebGLRenderingContextErrorMessageCallback;
     friend class WebGLVertexArrayObjectOES;
 
-    WebGLRenderingContext(HTMLCanvasElement*, PassRefPtr<GraphicsContext3D>, GraphicsContext3D::Attributes);
+    WebGLRenderingContext(HTMLCanvasElement*, PassRefPtr<GraphicsContext3D>, GraphicsContext3D::Attributes, GraphicsContext3D::Attributes);
     void initializeNewContext();
     void setupFlags();
 
@@ -493,6 +497,7 @@ public:
     bool m_contextLost;
     LostContextMode m_contextLostMode;
     GraphicsContext3D::Attributes m_attributes;
+    GraphicsContext3D::Attributes m_requestedAttributes;
 
     bool m_layerCleared;
     GC3Dfloat m_clearColor[4];
@@ -769,6 +774,20 @@ public:
     void restoreCurrentFramebuffer();
     void restoreCurrentTexture2D();
 
+    class WebGLMultisamplingChangedObserver : public Page::MultisamplingChangedObserver, public RefCounted<WebGLMultisamplingChangedObserver> {
+    public:
+        WebGLMultisamplingChangedObserver(WebGLRenderingContext*, Page*);
+        virtual void multisamplingChanged(bool);
+        virtual ~WebGLMultisamplingChangedObserver();
+
+    private:
+        WebGLRenderingContext* m_context;
+        Page* m_page;
+        bool m_multisamplingAllowed;
+    };
+
+    RefPtr<WebGLMultisamplingChangedObserver> m_multisamplingChangedObserver;
+
     friend class WebGLStateRestorer;
     friend class WebGLRenderingContextEvictionManager;