Allow const& for SkImages and SkPictures in draw methods.

This is just a convenience for callers, since we are (strongly) encouraging them to use sk_sp<> for managing image objects (and pictures btw). No change under the hood, as we are keeping our agnostic approach to these for the protected virtuals (since often we don't want to ref the parameter).

BUG=skia:
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Review URL: https://codereview.chromium.org/1777403002
1 file changed