Got WebGLRenderingContextBase to work with the "implements" syntax

Source/core/html/canvas/WebGLRenderingContextBase.idl

 /*
  * 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 22 matching lines @@
 typedef long long      GLintptr;
 typedef long long      GLsizeiptr;
 typedef octet          GLubyte;        /* 'octet' should be an unsigned 8 bit type. */
 typedef unsigned short GLushort;
 typedef unsigned long  GLuint;
 typedef /*unrestricted*/ float GLfloat;
 typedef /*unrestricted*/ float GLclampf;
 
 [
     DoNotCheckConstants,
+    ImplementedInBaseClass,
+    NoInterfaceObject,
     StrictTypeChecking,
-    NoInterfaceObject
 ] interface WebGLRenderingContextBase {
 
     readonly attribute HTMLCanvasElement canvas;
 
     /* ClearBufferMask */
     const GLenum DEPTH_BUFFER_BIT               = 0x00000100;
     const GLenum STENCIL_BUFFER_BIT             = 0x00000400;
     const GLenum COLOR_BUFFER_BIT               = 0x00004000;
 
     /* BeginMode */
@@ skipping 613 matching lines @@
     [Custom] void vertexAttrib2fv(GLuint indx, Float32Array values);
     void vertexAttrib3f(GLuint indx, GLfloat x, GLfloat y, GLfloat z);
     [Custom] void vertexAttrib3fv(GLuint indx, Float32Array values);
     void vertexAttrib4f(GLuint indx, GLfloat x, GLfloat y, GLfloat z, GLfloat w);
     [Custom] void vertexAttrib4fv(GLuint indx, Float32Array values);
     void vertexAttribPointer(GLuint indx, GLint size, GLenum type, GLboolean normalized,
                              GLsizei stride, GLintptr offset);
 
     void viewport(GLint x, GLint y, GLsizei width, GLsizei height);
 };