GN: more optional components: jpeg, pdf, png, xml

src/codec/SkPngCodec.h

Index: src/codec/SkPngCodec.h
diff --git a/src/codec/SkPngCodec.h b/src/codec/SkPngCodec.h
index aace7b1c4cedabaf0548ce90e2b48648ce1e0139..7bb833d10d836fc45f7663b1c1af92063306f2e8 100644
--- a/src/codec/SkPngCodec.h
+++ b/src/codec/SkPngCodec.h
@@ -14,7 +14,11 @@
 #include "SkRefCnt.h"
 #include "SkSwizzler.h"
 
-#include "png.h"
+// Instead of including png.h here, forward declare the few types we refer to.

[msarett, 2016/08/24 16:41:51]

This should work.  I believe we've had issues in the past because old versions
of libpng used different names for these structs.

We are working towards requiring 1.6 now.

Might want to use CMake trybots though.

+struct png_struct_def;
+struct png_info_def;
+typedef png_struct_def png_struct;
+typedef png_info_def png_info;
 
 class SkStream;
 
@@ -47,11 +51,11 @@ protected:
                          int startRow) = 0;
 
     SkPngCodec(const SkEncodedInfo&, const SkImageInfo&, SkStream*, SkPngChunkReader*,
-            png_structp, png_infop, int, int);
+               png_struct*, png_info*, int, int);
 
     SkAutoTUnref<SkPngChunkReader>     fPngChunkReader;
-    png_structp                        fPng_ptr;
-    png_infop                          fInfo_ptr;
+    png_struct*                        fPng_ptr;
+    png_info*                          fInfo_ptr;
 
     // These are stored here so they can be used both by normal decoding and scanline decoding.
     SkAutoTUnref<SkColorTable>         fColorTable;    // May be unpremul.