Have bindings layer assume and insist that all interface types are GCed.

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

 // 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.
 
 typedef unsigned long  GLenum;
 typedef boolean        GLboolean;
 typedef unsigned long  GLbitfield;
 typedef byte           GLbyte; // 'byte' should be a signed 8 bit type.
 typedef short          GLshort;
 typedef long           GLint;
 typedef long           GLsizei;
 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;
 typedef long long      GLint64;
 
 [
     RuntimeEnabled=UnsafeES3APIs,
     NoInterfaceObject,
-    GarbageCollected,
 ] interface WebGL2RenderingContextBase {
     const GLenum READ_BUFFER                                   = 0x0C02;
     const GLenum UNPACK_ROW_LENGTH                             = 0x0CF2;
     const GLenum UNPACK_SKIP_ROWS                              = 0x0CF3;
     const GLenum UNPACK_SKIP_PIXELS                            = 0x0CF4;
     const GLenum PACK_ROW_LENGTH                               = 0x0D02;
     const GLenum PACK_SKIP_ROWS                                = 0x0D03;
     const GLenum PACK_SKIP_PIXELS                              = 0x0D04;
     const GLenum COLOR                                         = 0x1800;
     const GLenum DEPTH                                         = 0x1801;
@@ skipping 406 matching lines @@
     /* Vertex Array Objects */
     WebGLVertexArrayObject createVertexArray();
     [CallWith=ScriptState] void deleteVertexArray(WebGLVertexArrayObject? vertexArray);
     GLboolean isVertexArray(WebGLVertexArrayObject? vertexArray);
     [CallWith=ScriptState] void bindVertexArray(WebGLVertexArrayObject? vertexArray);
 
     /* Reading */
     void readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLintptr offset);
 };
 WebGL2RenderingContextBase implements WebGLRenderingContextBase;