Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLDepthTexture.cpp

 /*
  * Copyright (C) 2012 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 @@
 
 WebGLDepthTexture::~WebGLDepthTexture()
 {
 }
 
 WebGLExtension::ExtensionName WebGLDepthTexture::getName() const
 {
     return WebGLDepthTextureName;
 }
 
-PassOwnPtr<WebGLDepthTexture> WebGLDepthTexture::create(WebGLRenderingContext* context)
+PassRefPtr<WebGLDepthTexture> WebGLDepthTexture::create(WebGLRenderingContext* context)
 {
-    return adoptPtr(new WebGLDepthTexture(context));
+    return adoptRef(new WebGLDepthTexture(context));
 }
 
 bool WebGLDepthTexture::supported(WebGLRenderingContext* context)
 {
     Extensions3D* extensions = context->graphicsContext3D()->getExtensions();
     // Emulating the UNSIGNED_INT_24_8_WEBGL texture internal format in terms
     // of two separate texture objects is too difficult, so disable depth
     // textures unless a packed depth/stencil format is available.
     if (!extensions->supports("GL_OES_packed_depth_stencil"))
         return false;
     return extensions->supports("GL_CHROMIUM_depth_texture")
         || extensions->supports("GL_OES_depth_texture")
         || extensions->supports("GL_ARB_depth_texture");
 }
 
 const char* WebGLDepthTexture::getExtensionName()
 {
     return "WEBGL_depth_texture";
 }
 
 } // namespace WebCore