Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/EXTDrawBuffers.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 17 matching lines @@
 #include "core/html/canvas/EXTDrawBuffers.h"
 
 #include "core/platform/graphics/Extensions3D.h"
 
 namespace WebCore {
 
 EXTDrawBuffers::EXTDrawBuffers(WebGLRenderingContext* context)
     : WebGLExtension(context)
 {
     ScriptWrappable::init(this);
-    context->graphicsContext3D()->getExtensions()->ensureEnabled("GL_EXT_draw_buffers");
+    enable();
 }
 
 EXTDrawBuffers::~EXTDrawBuffers()
 {
 }
 
+void EXTDrawBuffers::enable()
+{
+    m_context->graphicsContext3D()->getExtensions()->ensureEnabled("GL_EXT_draw_buffers");
+}
+
 WebGLExtension::ExtensionName EXTDrawBuffers::getName() const
 {
     return WebGLExtension::EXTDrawBuffersName;
 }
 
 PassOwnPtr<EXTDrawBuffers> EXTDrawBuffers::create(WebGLRenderingContext* context)
 {
     return adoptPtr(new EXTDrawBuffers(context));
 }
 
 // static
 bool EXTDrawBuffers::supported(WebGLRenderingContext* context)
 {
     Extensions3D* extensions = context->graphicsContext3D()->getExtensions();
     return (extensions->supports("GL_EXT_draw_buffers")
         && satisfiesWebGLRequirements(context));
 }
 
 const char* EXTDrawBuffers::getExtensionName()
 {
     return "EXT_draw_buffers";
 }
 
 void EXTDrawBuffers::drawBuffersEXT(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, "drawBuffersEXT", "more than one buffer");
             return;
         }
         if (bufs[0] != GraphicsContext3D::BACK && bufs[0] != GraphicsContext3D::NONE) {
             m_context->synthesizeGLError(GraphicsContext3D::INVALID_OPERATION, "drawBuffersEXT", "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