SkPDF:  fix PDF/A

TODO: get a bot to start testing this.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1864163004

Review URL: https://codereview.chromium.org/1864163004
diff --git a/src/pdf/SkPDFMetadata.cpp b/src/pdf/SkPDFMetadata.cpp
index addec4f..5a1d7aa 100644
--- a/src/pdf/SkPDFMetadata.cpp
+++ b/src/pdf/SkPDFMetadata.cpp
@@ -52,9 +52,6 @@
     return dict.release();
 }
 
-#undef SKPDF_STRING
-#undef SKPDF_STRING_IMPL
-
 #ifdef SK_PDF_GENERATE_PDFA
 SkPDFMetadata::UUID SkPDFMetadata::uuid() const {
     // The main requirement is for the UUID to be unique; the exact
@@ -297,7 +294,7 @@
             "%s"  // keywords
             "<xmpMM:DocumentID>uuid:%s</xmpMM:DocumentID>\n"
             "<xmpMM:InstanceID>uuid:%s</xmpMM:InstanceID>\n"
-            "<pdf:Producer>Skia/PDF</pdf:Producer>\n"
+            "<pdf:Producer>Skia/PDF m" SKPDF_STRING(SK_MILESTONE) "</pdf:Producer>\n"
             "%s"  // pdf:Keywords
             "</rdf:Description>\n"
             "</rdf:RDF>\n"
@@ -356,3 +353,7 @@
 }
 
 #endif  // SK_PDF_GENERATE_PDFA
+
+#undef SKPDF_STRING
+#undef SKPDF_STRING_IMPL
+