<http://webkit.org/b/65076> / <rdar://problem/9606246>

WebKit2 printing works by having the web process render the page content to a PDF. The PDF
data is then shipped to the UI process which will render it in to the printing graphics context.
Links were being lost because the API used to do the rendering of the PDF in to the printing
graphics context, CGContextDrawPDFPage, did not preserve the links that were present in the
PDF content received from the web process.

To fix this we switch to using PDFKit for drawing the PDF in to the printing graphics context.
PDFKit provides the ability for us to iterate over the links in the PDF content ourselves and
add links in to the printing graphics context.

Reviewed by Alexey Proskuryakov.

* UIProcess/API/mac/WKPrintingView.h:
* UIProcess/API/mac/WKPrintingView.mm:
(pdfAnnotationLinkClass): Look up the PDFAnnotationLink class from PDFKit as WebKit2 loads PDFKit lazily.
(pdfDocumentClass): Ditto.
(-[WKPrintingView _drawPDFDocument:page:atPoint:]): Switch to using the PDFKit equivalents of several types.
Iterate over the annotations present in the PDFPage, calling CGPDFContextSetURLForRect for each PDFAnnotationLink
that we find.
(-[WKPrintingView _drawPreview:]): Create an NSData to feed to PDFDocument.
(-[WKPrintingView drawRect:]): Ditto.
* WebKit2Prefix.h: Add the usual workaround to make Objective-C exceptions compile when C++ exception handling is disabled.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@104377 268f45cc-cd09-0410-ab3c-d52691b4dbfc