Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLDrawBuffers.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 29 matching lines @@
 
 WebGLDrawBuffers::~WebGLDrawBuffers()
 {
 }
 
 WebGLExtension::ExtensionName WebGLDrawBuffers::getName() const
 {
     return WebGLExtension::WebGLDrawBuffersName;
 }
 
-PassOwnPtr<WebGLDrawBuffers> WebGLDrawBuffers::create(WebGLRenderingContext* context)
+PassRefPtr<WebGLDrawBuffers> WebGLDrawBuffers::create(WebGLRenderingContext* context)
 {
-    return adoptPtr(new WebGLDrawBuffers(context));
+    return adoptRef(new WebGLDrawBuffers(context));
 }
 
 // static
 bool WebGLDrawBuffers::supported(WebGLRenderingContext* context)
 {
     Extensions3D* extensions = context->graphicsContext3D()->getExtensions();
     return (extensions->supports("GL_EXT_draw_buffers")
         && satisfiesWebGLRequirements(context));
 }
 
 const char* WebGLDrawBuffers::getExtensionName()
 {
     return "WEBGL_draw_buffers";
 }
 
 void WebGLDrawBuffers::drawBuffersWEBGL(const Vector<GC3Denum>& buffers)
 {
-    if (m_context->isContextLost())
+    if (isLost())
         return;
     GC3Dsizei n = buffers.size();
     const GC3Denum* bufs = buffers.data();
     if (!m_context->m_framebufferBinding) {
         if (n != 1) {
             m_context->synthesizeGLError(GraphicsContext3D::INVALID_VALUE, "drawBuffersWEBGL", "more than one buffer");
             return;
         }
         if (bufs[0] != GraphicsContext3D::BACK && bufs[0] != GraphicsContext3D::NONE) {
             m_context->synthesizeGLError(GraphicsContext3D::INVALID_OPERATION, "drawBuffersWEBGL", "BACK or NONE");
@@ skipping 92 matching lines @@
     if (supportsDepth)
         context->deleteTexture(depth);
     if (supportsDepthStencil)
         context->deleteTexture(depthStencil);
     for (size_t i = 0; i < colors.size(); ++i)
         context->deleteTexture(colors[i]);
     return ok;
 }
 
 } // namespace WebCore