[WebGL 2] primitive restart should be always enabled

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 969 matching lines @@
 
     webContext()->viewport(0, 0, drawingBufferWidth(), drawingBufferHeight());
     webContext()->scissor(0, 0, drawingBufferWidth(), drawingBufferHeight());
 
     m_contextLostCallbackAdapter = WebGLRenderingContextLostCallback::create(this);
     m_errorMessageCallbackAdapter = WebGLRenderingContextErrorMessageCallback::create(this);
 
     webContext()->setContextLostCallback(m_contextLostCallbackAdapter.get());
     webContext()->setErrorMessageCallback(m_errorMessageCallbackAdapter.get());
 
+    // If WebGL 2, the PRIMITIVE_RESTART_FIXED_INDEX should be always enabled.
+    // See the section <Primitive Restart is Always Enabled> in WebGL 2 spec:
+    // https://www.khronos.org/registry/webgl/specs/latest/2.0/#4.1.4
+    if (isWebGL2OrHigher())
+        webContext()->enable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
+
     // This ensures that the context has a valid "lastFlushID" and won't be mistakenly identified as the "least recently used" context.
     webContext()->flush();
 
     for (int i = 0; i < WebGLExtensionNameCount; ++i)
         m_extensionEnabled[i] = false;
 
     m_isWebGL2FormatsTypesAdded = false;
     m_isWebGL2InternalFormatsCopyTexImageAdded = false;
     m_isOESTextureFloatFormatsTypesAdded = false;
     m_isOESTextureHalfFloatFormatsTypesAdded = false;
@@ skipping 5285 matching lines @@
         webContext()->pixelStorei(GL_UNPACK_ALIGNMENT, 1);
 }
 
 void WebGLRenderingContextBase::restoreUnpackParameters()
 {
     if (m_unpackAlignment != 1)
         webContext()->pixelStorei(GL_UNPACK_ALIGNMENT, m_unpackAlignment);
 }
 
 } // namespace blink