Revert of rename SkCanvasDrawable to SkDrawable, and make public

src/core/SkCanvasDrawable.h

Index: src/core/SkCanvasDrawable.h
diff --git a/src/core/SkCanvasDrawable.h b/src/core/SkCanvasDrawable.h
new file mode 100644
index 0000000000000000000000000000000000000000..bc5b4fd351e6513d08bf341c6e464e67d967991b
--- /dev/null
+++ b/src/core/SkCanvasDrawable.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCanvasDrawable_DEFINED
+#define SkCanvasDrawable_DEFINED
+
+#include "SkRefCnt.h"
+
+class SkCanvas;
+class SkPicture;
+struct SkRect;
+
+/**
+ *  Base-class for objects that draw into SkCanvas.
+ *
+ *  The object has a generation ID, which is guaranteed to be unique across all drawables. To
+ *  allow for clients of the drawable that may want to cache the results, the drawable must
+ *  change its generation ID whenever its internal state changes such that it will draw differently.
+ */
+class SkCanvasDrawable : public SkRefCnt {
+public:
+    SkCanvasDrawable();
+
+    /**
+     *  Draws into the specified content. The drawing sequence will be balanced upon return
+     *  (i.e. the saveLevel() on the canvas will match what it was when draw() was called,
+     *  and the current matrix and clip settings will not be changed.
+     */
+    void draw(SkCanvas*);
+
+    SkPicture* newPictureSnapshot();
+
+    /**
+     *  Return a unique value for this instance. If two calls to this return the same value,
+     *  it is presumed that calling the draw() method will render the same thing as well.
+     *
+     *  Subclasses that change their state should call notifyDrawingChanged() to ensure that
+     *  a new value will be returned the next time it is called.
+     */
+    uint32_t getGenerationID();
+
+    /**
+     *  Return the (conservative) bounds of what the drawable will draw. If the drawable can
+     *  change what it draws (e.g. animation or in response to some external change), then this
+     *  must return a bounds that is always valid for all possible states.
+     */
+    SkRect getBounds();
+
+    /**
+     *  Calling this invalidates the previous generation ID, and causes a new one to be computed
+     *  the next time getGenerationID() is called. Typically this is called by the object itself,
+     *  in response to its internal state changing.
+     */
+    void notifyDrawingChanged();
+
+protected:
+    virtual SkRect onGetBounds() = 0;
+    virtual void onDraw(SkCanvas*) = 0;
+    virtual SkPicture* onNewPictureSnapshot();
+
+private:
+    int32_t fGenerationID;
+};
+
+#endif