SkCodec: add wbmp class

src/codec/SkCodec_wbmp.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCodec_wbmp_DEFINED
+#define SkCodec_wbmp_DEFINED
+
+#include "SkCodec.h"
+
+class SkWbmpCodec final : public SkCodec {
+public:
+    static bool IsWbmp(SkStream*);
+    static SkCodec* NewFromStream(SkStream*);
+protected:
+    SkEncodedFormat onGetEncodedFormat() const override;
+    Result onGetPixels(const SkImageInfo&, void*, size_t,
+                       const Options&, SkPMColor[], int*) override;
+private:
+    SkWbmpCodec(const SkImageInfo&, SkStream*);
+};
+
+#endif  // SkCodec_wbmp_DEFINED