RFR: 8202990: javafx webview css filter property with display scaling

[Kevin Rushforth]

On Tue, 11 Aug 2020 16:18:37 GMT, Bhawesh Choudhary <bchoudhary at openjdk.org> wrote:

> ImageJava.cpp ignores CompositeOperator parameter in drawImage function due to which shadow was getting drawn on top of
> actual image. apply given composite operator to graphics context before drawing image to fix this issue. another issue
> is into WCGraphicsPrismContext.java. while blending two layers, applying state to the destination layer was missed due
> to which image was not getting drawn with right scale in hidpi mode. apply state to fix the issue.

With your patch installed, I see a race condition that manifests in one of two ways:

* If I load the new .html file with HelloWebView, I see the shadow most of the time, but it is messing some of the time.
* The new unit test crashes intermittently

I suspect this might be related to the `gc.setCompositeOperation` call. Are you certain this is being done on the right
thread?

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Changes requested by kcr (Lead).

PR: https://git.openjdk.java.net/jfx/pull/279