add colortable support to imagegenerator

src/lazy/SkDiscardablePixelRef.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDiscardablePixelRef_DEFINED
 #define SkDiscardablePixelRef_DEFINED
 
 #include "SkDiscardableMemory.h"
 #include "SkImageGenerator.h"
 #include "SkImageInfo.h"
 #include "SkPixelRef.h"
 
 /**
  *  A PixelRef backed by SkDiscardableMemory, with the ability to
  *  re-generate the pixels (via a SkImageGenerator) if the DM is
  *  purged.
- *
- *  Since SkColorTable is reference-counted, we do not support indexed
- *  color with this class; there would be no way for the discardable
- *  memory system to unref the color table.
  */
 class SkDiscardablePixelRef : public SkPixelRef {
 public:
     SK_DECLARE_INST_COUNT(SkDiscardablePixelRef)
     SK_DECLARE_UNFLATTENABLE_OBJECT()
 
 protected:
     ~SkDiscardablePixelRef();
 
     virtual bool onNewLockPixels(LockRec*) SK_OVERRIDE;
     virtual void onUnlockPixels() SK_OVERRIDE;
     virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }
 
     virtual SkData* onRefEncodedData() SK_OVERRIDE {
         return fGenerator->refEncodedData();
     }
 
 private:
     SkImageGenerator* const fGenerator;
     SkDiscardableMemory::Factory* const fDMFactory;
     const size_t fRowBytes;
     // These const members should not change over the life of the
     // PixelRef, since the SkBitmap doesn't expect them to change.
 
     SkDiscardableMemory* fDiscardableMemory;
+    SkAutoTUnref<SkColorTable> fCTable;
 
     /* Takes ownership of SkImageGenerator. */
     SkDiscardablePixelRef(const SkImageInfo&, SkImageGenerator*,
                           size_t rowBytes,
                           SkDiscardableMemory::Factory* factory);
 
     friend bool SkInstallDiscardablePixelRef(SkImageGenerator*, SkBitmap*,
                                              SkDiscardableMemory::Factory*);
 
     typedef SkPixelRef INHERITED;
 };
 
 #endif  // SkDiscardablePixelRef_DEFINED