SkDeflateWStream: support gzip output

src/pdf/SkDeflate.h

Index: src/pdf/SkDeflate.h
diff --git a/src/pdf/SkDeflate.h b/src/pdf/SkDeflate.h
index 129d1bf8c3c7fe4203ca5cdc8e4c93c0722e773a..978b57edaf6ada9d7b3b8ee22bad8e8ff021e024 100644
--- a/src/pdf/SkDeflate.h
+++ b/src/pdf/SkDeflate.h
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2010 The Android Open Source Project
  *
@@ -16,15 +15,26 @@
 
 /**
   * Wrap a stream in this class to compress the information written to
-  * this stream using the Deflate algorithm.  Uses Zlib's
-  * Z_DEFAULT_COMPRESSION level.
+  * this stream using the Deflate algorithm.
   *
   * See http://en.wikipedia.org/wiki/DEFLATE
   */
 class SkDeflateWStream final : public SkWStream {
 public:
-    /** Does not take ownership of the stream. */
-    SkDeflateWStream(SkWStream*);
+    /** Does not take ownership of the stream.
+
+        @param compressionLevel - 0 is no compression; 1 is best
+        speed; 9 is best compression.  The default, -1, is to use
+        zlib's Z_DEFAULT_COMPRESSION level.
+
+        @param gzip iff true, output a gzip file. "The gzip format is
+        a wrapper, documented in RFC 1952, around a deflate stream."
+        gzip adds a header with a magic number to the beginning of the
+        stream, alowing a client to identify a gzip file.
+     */
+    SkDeflateWStream(SkWStream*,
+                     int compressionLevel = -1,
+                     bool gzip = false);
 
     /** The destructor calls finalize(). */
     ~SkDeflateWStream();