Scanline decoding for wbmp

src/codec/SkCodec_wbmp.h

Index: src/codec/SkCodec_wbmp.h
diff --git a/src/codec/SkCodec_wbmp.h b/src/codec/SkCodec_wbmp.h
index fece249728e72e1f2d0fcd0700981a84a116a8da..cec398d34b8e036a9574b4d09d6d046fa278be20 100644
--- a/src/codec/SkCodec_wbmp.h
+++ b/src/codec/SkCodec_wbmp.h
@@ -9,17 +9,53 @@
 #define SkCodec_wbmp_DEFINED
 
 #include "SkCodec.h"
+#include "SkScanlineDecoder.h"
+#include "SkSwizzler.h"
 
 class SkWbmpCodec final : public SkCodec {
 public:
     static bool IsWbmp(SkStream*);
+
+    /*
+     * Assumes IsWbmp was called and returned true
+     * Creates a wbmp codec
+     * Takes ownership of the stream
+     */
     static SkCodec* NewFromStream(SkStream*);
+
+    /*
+     * Assumes IsWbmp was called and returned true
+     * Creates a wbmp scanline decoder
+     * Takes ownership of the stream
+     */
+    static SkScanlineDecoder* NewSDFromStream(SkStream*);
 protected:
     SkEncodedFormat onGetEncodedFormat() const override;
     Result onGetPixels(const SkImageInfo&, void*, size_t,
                        const Options&, SkPMColor[], int*) override;
 private:
+
+    /*
+     * Calls rewindIfNeeded and returns true if the decoder can continue
+     */
+    bool handleRewind();
+
+    /*
+     * Returns a swizzler on success, NULL on failure
+     */
+    SkSwizzler* initializeSwizzler(const SkImageInfo& info, const SkPMColor* ctable,
+                                   const Options& opts);
+
+    /*
+     * Read a src row from the encoded stream
+     */
+    Result readRow(uint8_t* row);
+
     SkWbmpCodec(const SkImageInfo&, SkStream*);
+
+    const size_t fSrcRowBytes;
+
+    friend class SkWbmpScanlineDecoder;
     typedef SkCodec INHERITED;
 };