Make WebGLRenderingContext.getAttachedShaders() return type nullable

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 527 matching lines @@
     void finish();
     void flush();
     void framebufferRenderbuffer(GLenum target, GLenum attachment, GLenum renderbuffertarget, WebGLRenderbuffer? renderbuffer);
     void framebufferTexture2D(GLenum target, GLenum attachment, GLenum textarget, WebGLTexture? texture, GLint level);
     void frontFace(GLenum mode);
     void generateMipmap(GLenum target);
 
     WebGLActiveInfo getActiveAttrib(WebGLProgram? program, GLuint index);
     WebGLActiveInfo getActiveUniform(WebGLProgram? program, GLuint index);
 
-    [Custom] void getAttachedShaders(WebGLProgram? program);
+    sequence<WebGLShader>? getAttachedShaders(WebGLProgram? program);
 
     GLint getAttribLocation(WebGLProgram? program, DOMString name);
 
     [Custom] any getBufferParameter(GLenum target, GLenum pname);
 
     WebGLContextAttributes getContextAttributes();
 
     GLenum getError();
 
     // object getExtension(DOMString name);
@@ skipping 121 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);
 };