Provide a pointer to SecurityOrigin within SVGFEImageElement so that
it can test if its content actually taints the origin. Previously all
filters with feImages tainted the canvas. When the filter is set
(during CanvasRenderingContext2DState::SetFilter) the SecurityOrigin
is stored. During CanvasRenderingContext2DState::GetFilter is it
determined whether the compiled filter should taint the canvas.

Next step is to make this work for other svg_fe elements.

Change the test expectations for SVGFEDisplacment tests as FEImages
no longer necessarily taint the origin. Reverting changes here:
https://chromium-review.googlesource.com/c/chromium/src/+/782649/

Bug: 618871
Change-Id: I506c443f842068f08eab0e3d6b214f2b10878a86
Reviewed-on: https://chromium-review.googlesource.com/c/1258968
Commit-Queue: Aaron Krajeski <aaronhk@chromium.org>
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608934}