remove picture-backed surfaces

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 171 matching lines @@
      *        sometimes.
      */
 #ifndef SK_SUPPORT_LEGACY_GETTOPDEVICE
 private:
 #endif
     SkBaseDevice* getTopDevice(bool updateMatrixClip = false) const;
 public:
 
     /**
      *  Create a new surface matching the specified info, one that attempts to
-     *  be maximally compatible when used with this canvas.
+     *  be maximally compatible when used with this canvas. If there is no matching Surface type,
+     *  NULL is returned.
      */
     SkSurface* newSurface(const SkImageInfo&);
 
     /**
      * Return the GPU context of the device that is associated with the canvas.
      * For a canvas with non-GPU device, NULL is returned.
      */
     GrContext* getGrContext();
 
     ///////////////////////////////////////////////////////////////////////////
@@ skipping 1226 matching lines @@
     bool asROBitmap(SkBitmap*) const;
 
 private:
     SkBitmap    fBitmap;    // used if peekPixels() fails
     const void* fAddr;      // NULL on failure
     SkImageInfo fInfo;
     size_t      fRowBytes;
 };
 
 #endif