Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLCompressedTexturePVRTC.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 18 matching lines @@
 
 #include "core/html/canvas/WebGLRenderingContext.h"
 #include "core/platform/graphics/Extensions3D.h"
 
 namespace WebCore {
 
 WebGLCompressedTexturePVRTC::WebGLCompressedTexturePVRTC(WebGLRenderingContext* context)
     : WebGLExtension(context)
 {
     ScriptWrappable::init(this);
-    context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGB_PVRTC_4BPPV1_IMG);
-    context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGB_PVRTC_2BPPV1_IMG);
-    context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGBA_PVRTC_4BPPV1_IMG);
-    context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGBA_PVRTC_2BPPV1_IMG);
+    enable();
 }
 
 WebGLCompressedTexturePVRTC::~WebGLCompressedTexturePVRTC()
 {
 }
 
+void WebGLCompressedTexturePVRTC::enable()
+{
+    m_context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGB_PVRTC_4BPPV1_IMG);
+    m_context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGB_PVRTC_2BPPV1_IMG);
+    m_context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGBA_PVRTC_4BPPV1_IMG);
+    m_context->addCompressedTextureFormat(Extensions3D::COMPRESSED_RGBA_PVRTC_2BPPV1_IMG);
+}
+
 WebGLExtension::ExtensionName WebGLCompressedTexturePVRTC::getName() const
 {
     return WebGLCompressedTexturePVRTCName;
 }
 
 PassOwnPtr<WebGLCompressedTexturePVRTC> WebGLCompressedTexturePVRTC::create(WebGLRenderingContext* context)
 {
     return adoptPtr(new WebGLCompressedTexturePVRTC(context));
 }
 
 bool WebGLCompressedTexturePVRTC::supported(WebGLRenderingContext* context)
 {
     Extensions3D* extensions = context->graphicsContext3D()->getExtensions();
     return extensions->supports("GL_IMG_texture_compression_pvrtc");
 }
 
 const char* WebGLCompressedTexturePVRTC::getExtensionName()
 {
     return "WEBGL_compressed_texture_pvrtc";
 }
 
 } // namespace WebCore