[RFR] JDK-8208622: [WebView] IllegalStateException when invoking print API with html form controls

[Arunprasad Rajkumar]

Hi,

Please review the fix for following bug,

https://bugs.openjdk.java.net/browse/JDK-8208622

Root cause:
`RenderThemeJava` instance is associated with form controls rendering in `WebPage::prePaint` and disassociated in `WebPage::postPaint`. However, when printing is invoked, `WebPage.print` directly invokes `WebPage::paint` without invoking `WebPage::prePaint`, which causes the exception because there is no valid `RenderThemeJava` instance is available to render form controls.

Proposed solution:
Associate java `RenderTheme` instance with `PlatformContextJava` and make use of it while rendering FormControls. This solution also eliminates global state.

Webrev:
http://cr.openjdk.java.net/~arajkumar/8208622/webrev

Regards,
Arun