Add SkSpecialImage::extractSubset & NewFromPixmap

src/core/SkAutoPixmapStorage.h

Index: src/core/SkAutoPixmapStorage.h
diff --git a/src/core/SkAutoPixmapStorage.h b/src/core/SkAutoPixmapStorage.h
new file mode 100644
index 0000000000000000000000000000000000000000..4379b13d2482ade8ed7c5f8bc48751be460caee6
--- /dev/null
+++ b/src/core/SkAutoPixmapStorage.h
@@ -0,0 +1,87 @@
+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAutoPixmapStorage_DEFINED
+#define SkAutoPixmapStorage_DEFINED
+
+#include "SkPixmap.h"
+
+class SK_API SkAutoPixmapStorage : public SkPixmap {
+public:
+    SkAutoPixmapStorage();
+    ~SkAutoPixmapStorage();
+
+    /**
+    *  Try to allocate memory for the pixels needed to match the specified Info. On success
+    *  return true and fill out the pixmap to point to that memory. The storage will be freed
+    *  when this object is destroyed, or if another call to tryAlloc() or alloc() is made.
+    *
+    *  On failure, return false and reset() the pixmap to empty.
+    */
+    bool tryAlloc(const SkImageInfo&);
+
+    /**
+    *  Allocate memory for the pixels needed to match the specified Info and fill out the pixmap
+    *  to point to that memory. The storage will be freed when this object is destroyed,
+    *  or if another call to tryAlloc() or alloc() is made.
+    *
+    *  If the memory cannot be allocated, calls sk_throw().
+    */
+    void alloc(const SkImageInfo&);
+
+    /**
+    * Gets the size and optionally the rowBytes that would be allocated by SkAutoPixmapStorage if
+    * alloc/tryAlloc was called.
+    */
+    static size_t AllocSize(const SkImageInfo& info, size_t* rowBytes);
+
+    /**
+    *  Returns an SkData object wrapping the allocated pixels memory, and resets the pixmap.
+    *  If the storage hasn't been allocated, the result is NULL.
+    */
+    const SkData* SK_WARN_UNUSED_RESULT detachPixelsAsData();
+
+    /**
+    * Whereas 'reset' frees the backing memory and then clears the SkPixmap,
+    * this entry point disowns the backing memory before clearing so the memory
+    * isn't freed. It can be used when the Pixmap has been installed into
+    * an SkBitmap and the SkBitmap should manage the memory's lifetime.
+    */
+    void release();
+
+    // We wrap these so we can clear our internal storage
+
+    void reset() {
+        this->freeStorage();
+        this->INHERITED::reset();
+    }
+    void reset(const SkImageInfo& info, const void* addr, size_t rb, SkColorTable* ctable = NULL) {
+        this->freeStorage();
+        this->INHERITED::reset(info, addr, rb, ctable);
+    }
+    void reset(const SkImageInfo& info) {
+        this->freeStorage();
+        this->INHERITED::reset(info);
+    }
+    bool SK_WARN_UNUSED_RESULT reset(const SkMask& mask) {
+        this->freeStorage();
+        return this->INHERITED::reset(mask);
+    }
+
+private:
+    void*   fStorage;
+
+    void freeStorage() {
+        sk_free(fStorage);
+        fStorage = nullptr;
+    }
+
+    typedef SkPixmap INHERITED;
+};
+
+#endif