Adds SVGImageElement as a CanvasImageSource

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl
index c599cbcd420dd7a089d214fcb6f0779c207c2079..2f37d674fa525e6738bdae13bcbdcc2130f2cefc 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.idl
@@ -25,8 +25,16 @@
 
 // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#canvasrenderingcontext2d
 
+// The spec specifies:
+//    typedef (HTMLImageElement or
+//             SVGImageElement) HTMLOrSVGImageElement;
+// but there's a problem with our IDL code generator for typedef-in-typedef,

[fs, 2017/03/13 13:56:34]

I saw crbug.com/700225, and that some fixes had landed there. Don't know if the
issue here was with nested unions of actually typedefs, anyway, might be worth
to revisit (here or in the ImageBitmapSource followup.)

[fserb, 2017/03/21 19:15:22]

Arghh, that took me a while to figure out. So, they've added support for it on
the IDL compiler, but I think the C++ generator is still not using it, so we are
still seeing broken behaviour when doing nested things. I'll keep the comment
and add a TODO for me to revisit this.

[fs, 2017/03/21 21:05:41]

Roger that.

+// so we split this into two for simplicity. There's no difference from a user
+// perspective.
+
 typedef (CSSImageValue or
          HTMLImageElement or
+         SVGImageElement or
          HTMLVideoElement or
          HTMLCanvasElement or
          ImageBitmap or