WebGL 2: validate read buffer attachment when reading from FBO

Source/core/html/canvas/WebGLFramebuffer.cpp

 /*
  * Copyright (C) 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 261 matching lines @@
 
 PassRefPtrWillBeRawPtr<WebGLFramebuffer> WebGLFramebuffer::create(WebGLRenderingContextBase* ctx)
 {
     return adoptRefWillBeNoop(new WebGLFramebuffer(ctx));
 }
 
 WebGLFramebuffer::WebGLFramebuffer(WebGLRenderingContextBase* ctx)
     : WebGLContextObject(ctx)
     , m_object(ctx->webContext()->createFramebuffer())
     , m_hasEverBeenBound(false)
+    , m_readBuffer(GL_COLOR_ATTACHMENT0)
 {
 }
 
 WebGLFramebuffer::~WebGLFramebuffer()
 {
     // Delete the platform framebuffer resource. Explicit detachment
     // is for the benefit of Oilpan, where the framebuffer object
     // isn't detached when it and the WebGLRenderingContextBase object
     // it is registered with are both finalized. Without Oilpan, the
     // object will have been detached.
@@ skipping 340 matching lines @@
 
 DEFINE_TRACE(WebGLFramebuffer)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_attachments);
 #endif
     WebGLContextObject::trace(visitor);
 }
 
 }