Fix the bug for VertexAttrib{I}Pointer when no array buffer bound

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/webgl/WebGL2RenderingContextBase.h"
 
 #include "bindings/modules/v8/WebGLAny.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLImageElement.h"
@@ skipping 2421 matching lines @@
                                                       long long offset) {
   if (isContextLost())
     return;
   if (index >= m_maxVertexAttribs) {
     synthesizeGLError(GL_INVALID_VALUE, "vertexAttribIPointer",
                       "index out of range");
     return;
   }
   if (!validateValueFitNonNegInt32("vertexAttribIPointer", "offset", offset))
     return;
-  if (!m_boundArrayBuffer) {
+  if (!m_boundArrayBuffer && offset != 0) {
     synthesizeGLError(GL_INVALID_OPERATION, "vertexAttribIPointer",
-                      "no bound ARRAY_BUFFER");
+                      "no ARRAY_BUFFER is bound and offset is non-zero");
     return;
   }
 
   m_boundVertexArrayObject->setArrayBufferForAttrib(index, m_boundArrayBuffer);
   contextGL()->VertexAttribIPointer(
       index, size, type, stride,
       reinterpret_cast<void*>(static_cast<intptr_t>(offset)));
 }
 
 /* Writing to the drawing buffer */
@@ skipping 2403 matching lines @@
 
 void WebGL2RenderingContextBase::
     DrawingBufferClientRestorePixelUnpackBufferBinding() {
   if (!contextGL())
     return;
   contextGL()->BindBuffer(GL_PIXEL_UNPACK_BUFFER,
                           objectOrZero(m_boundPixelUnpackBuffer.get()));
 }
 
 }  // namespace blink