FramebufferRenderbuffer() generates INVALID_OP if renderbuffer has never been bound.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.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 2501 matching lines @@
     GLenum renderbuffertarget,
     WebGLRenderbuffer* buffer) {
   if (isContextLost() || !ValidateFramebufferFuncParameters(
                              "framebufferRenderbuffer", target, attachment))
     return;
   if (renderbuffertarget != GL_RENDERBUFFER) {
     SynthesizeGLError(GL_INVALID_ENUM, "framebufferRenderbuffer",
                       "invalid target");
     return;
   }
-  if (buffer && !buffer->Validate(ContextGroup(), this)) {
+  if (buffer && (!buffer->HasEverBeenBound() ||
+                 !buffer->Validate(ContextGroup(), this))) {
     SynthesizeGLError(GL_INVALID_OPERATION, "framebufferRenderbuffer",
-                      "no buffer or buffer not from this context");
+                      "buffer never bound or buffer not from this context");
     return;
   }
   // Don't allow the default framebuffer to be mutated; all current
   // implementations use an FBO internally in place of the default
   // FBO.
   WebGLFramebuffer* framebuffer_binding = GetFramebufferBinding(target);
   if (!framebuffer_binding || !framebuffer_binding->Object()) {
     SynthesizeGLError(GL_INVALID_OPERATION, "framebufferRenderbuffer",
                       "no framebuffer bound");
     return;
@@ skipping 5248 matching lines @@
 void WebGLRenderingContextBase::getHTMLOrOffscreenCanvas(
     HTMLCanvasElementOrOffscreenCanvas& result) const {
   if (canvas()) {
     result.setHTMLCanvasElement(static_cast<HTMLCanvasElement*>(host()));
   } else {
     result.setOffscreenCanvas(static_cast<OffscreenCanvas*>(host()));
   }
 }
 
 }  // namespace blink