SkPDF: Fix links to be more valid PDF/A

src/pdf/SkPDFDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPDFDevice.h"
 
 #include "SkAnnotationKeys.h"
@@ skipping 809 matching lines @@
             }
             break;
         default:
             SkASSERT(false);
     }
 }
 
 static sk_sp<SkPDFDict> create_link_annotation(const SkRect& translatedRect) {
     auto annotation = sk_make_sp<SkPDFDict>("Annot");
     annotation->insertName("Subtype", "Link");
+    #ifdef SK_PDF_GENERATE_PDFA
+        annotation->insertInt("F", 4);  // required by ISO 19005
+    #endif
 
     auto border = sk_make_sp<SkPDFArray>();
     border->reserve(3);
     border->appendInt(0);  // Horizontal corner radius.
     border->appendInt(0);  // Vertical corner radius.
     border->appendInt(0);  // Width, 0 = no border.
     annotation->insertObject("Border", std::move(border));
 
     auto rect = sk_make_sp<SkPDFArray>();
     rect->reserve(4);
@@ skipping 1296 matching lines @@
         if (!pdfimage) {
             return;
         }
         fDocument->serialize(pdfimage);  // serialize images early.
         fDocument->canon()->addPDFBitmap(key, pdfimage);
     }
     // TODO(halcanary): addXObjectResource() should take a sk_sp<SkPDFObject>
     SkPDFUtils::DrawFormXObject(this->addXObjectResource(pdfimage.get()),
                                 &content.entry()->fContent);
 }