RFR: 8242861: Update ImagePattern to apply SVG pattern transforms

[Arun Joseph]

On Wed, 29 Apr 2020 06:45:04 GMT, Arun Joseph <ajoseph at openjdk.org> wrote:

>> Since this is in a common method used by all shapes, and not just WebView, we will need to ensure no regressions.
>
> All ImagePattern objects, other than the one from WebView, uses the second constructor which assigns an identity
> transform as the pattern transform. So, existing calls to PaintHelper concatenates the shader transform with an
> identity matrix and thus, shouldn't cause any regressions. Only calls from WebView's drawPattern() method in
> WCGraphicsPrismContext uses the patternTransform attribute.

The changes in drawPattern() forces the function to handle the operations for drawPattern (for images) and fillPattern
(for shapes) together. If required, a new opcode SET_FILL_PATTERN can be introduced for handling patterns in shapes and
part of the implementation can be seen from my previous commits to this PR.

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PR: https://git.openjdk.java.net/jfx/pull/190