change SkStreams to work with sk_sp<SkData> instead of SkData*

tests/PDFDocumentTest.cpp

Index: tests/PDFDocumentTest.cpp
diff --git a/tests/PDFDocumentTest.cpp b/tests/PDFDocumentTest.cpp
index c871375117cc13f5df2d289aeea0f3d8835b401f..afc05e49b885d5d91a7cac7c15d305cbeda7985e 100644
--- a/tests/PDFDocumentTest.cpp
+++ b/tests/PDFDocumentTest.cpp
@@ -193,8 +193,8 @@ DEF_TEST(SkPDF_pdfa_document, r) {
                                    pdfMetadata, nullptr, /* pdfa = */ true);
     doc->beginPage(64, 64)->drawColor(SK_ColorRED);
     doc->close();
-    sk_sp<SkData> data(buffer.copyToData());
-    buffer.reset();
+    sk_sp<SkData> data(buffer.detachAsData());
+
     static const char* expectations[] = {
         "sRGB IEC61966-2.1",
         "<dc:title><rdf:Alt><rdf:li xml:lang=\"x-default\">test document",
@@ -212,8 +212,7 @@ DEF_TEST(SkPDF_pdfa_document, r) {
                               pdfMetadata, nullptr, /* pdfa = */ true);
     doc->beginPage(64, 64)->drawColor(SK_ColorRED);
     doc->close();
-    data.reset(buffer.copyToData());
-    buffer.reset();
+    data = buffer.detachAsData();
 
     static const char* moreExpectations[] = {
         "/Producer (phoney library)",