SkPDF: SkPDFStream takes a unique_ptr

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2188623004

Review-Url: https://codereview.chromium.org/2188623004
diff --git a/src/pdf/SkPDFDocument.cpp b/src/pdf/SkPDFDocument.cpp
index 221f240..2b7eda1 100644
--- a/src/pdf/SkPDFDocument.cpp
+++ b/src/pdf/SkPDFDocument.cpp
@@ -278,8 +278,7 @@
     if (annotations->size() > 0) {
         page->insertObject("Annots", std::move(annotations));
     }
-    auto contentData = fPageDevice->content();
-    auto contentObject = sk_make_sp<SkPDFStream>(contentData.get());
+    auto contentObject = sk_make_sp<SkPDFStream>(fPageDevice->content());
     this->serialize(contentObject);
     page->insertObjRef("Contents", std::move(contentObject));
     fPageDevice->appendDestinations(fDests.get(), page.get());