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

third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.idl

 // Copyright 2016 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.
 
 // https://drafts.css-houdini.org/css-paint-api/#paintrenderingcontext2d
 
 [
     Exposed=PaintWorklet,
-    GarbageCollected,
     RuntimeEnabled=CSSPaintAPI,
 ] interface PaintRenderingContext2D {
     // state
     void save(); // push state on state stack
     void restore(); // pop state stack and restore state
 
     // transformations (default transform is the identity matrix)
     [RuntimeEnabled=ExperimentalCanvasFeatures] attribute SVGMatrix currentTransform;
     void scale(unrestricted double x, unrestricted double y);
     void rotate(unrestricted double angle);
@@ skipping 53 matching lines @@
     attribute DOMString lineCap; // "butt", "round", "square" (default "butt")
     attribute DOMString lineJoin; // "round", "bevel", "miter" (default "miter")
     attribute unrestricted double miterLimit; // (default 10)
 
     // dashed lines
     void setLineDash(sequence<unrestricted double> dash);
     sequence<unrestricted double> getLineDash();
     attribute unrestricted double lineDashOffset;
 };
 PaintRenderingContext2D implements CanvasPathMethods;