Use std::unique_ptr.

TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/20c1e3abfc681771f73eb19fde7284196e028940

Committed: https://skia.googlesource.com/skia/+/3dd9ed37c24611af86f0fe374bd3698b63f09450
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1780933003

Committed: https://skia.googlesource.com/skia/+/2691d76a06e1af6282f8b3a3140cc93361be10c4

Review URL: https://codereview.chromium.org/1780933003
diff --git a/src/pdf/SkPDFDevice.h b/src/pdf/SkPDFDevice.h
index b1345a8..b214839 100644
--- a/src/pdf/SkPDFDevice.h
+++ b/src/pdf/SkPDFDevice.h
@@ -168,7 +168,7 @@
 
     /** Returns a SkStream with the page contents.
      */
-    skstd::unique_ptr<SkStreamAsset> content() const;
+    std::unique_ptr<SkStreamAsset> content() const;
 
     /** Writes the page contents to the stream. */
     void writeContent(SkWStream*) const;