clarify that accessPixels is for write-access, and peekPixels is RO

include/core/SkDevice.h

 /*
  * Copyright 2010 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 SkDevice_DEFINED
 #define SkDevice_DEFINED
 
@@ skipping 64 matching lines @@
     /** Return the bitmap associated with this device. Call this each time you need
         to access the bitmap, as it notifies the subclass to perform any flushing
         etc. before you examine the pixels.
         @param changePixels set to true if the caller plans to change the pixels
         @return the device's bitmap
     */
     const SkBitmap& accessBitmap(bool changePixels);
 
     bool writePixels(const SkImageInfo&, const void*, size_t rowBytes, int x, int y);
 
+    /**
+     *  Try to get write-access to the pixels behind the device. If successful, this returns true
+     *  and fills-out the pixmap parameter. On success it also bumps the genID of the underlying
+     *  bitmap.
+     *
+     *  On failure, returns false and ignores the pixmap parameter.
+     */
     bool accessPixels(SkPixmap* pmap);
 
     /**
+     *  Try to get read-only-access to the pixels behind the device. If successful, this returns
+     *  true and fills-out the pixmap parameter.
+     *
+     *  On failure, returns false and ignores the pixmap parameter.
+     */
+    bool peekPixels(SkPixmap*);
+
+    /**
      * Return the device's associated gpu render target, or NULL.
      */
     virtual GrRenderTarget* accessRenderTarget() { return NULL; }
 
 
     /**
      *  Return the device's origin: its offset in device coordinates from
      *  the default origin in its canvas' matrix/clip
      */
     const SkIPoint& getOrigin() const { return fOrigin; }
@@ skipping 136 matching lines @@
     /** The SkDevice passed will be an SkDevice which was returned by a call to
         onCreateDevice on this device with kNeverTile_TileExpectation.
      */
     virtual void drawDevice(const SkDraw&, SkBaseDevice*, int x, int y,
                             const SkPaint&) = 0;
 
     virtual void drawTextOnPath(const SkDraw&, const void* text, size_t len, const SkPath&,
                                 const SkMatrix*, const SkPaint&);
 
     bool readPixels(const SkImageInfo&, void* dst, size_t rowBytes, int x, int y);
-    bool peekPixels(SkPixmap*);
 
     ///////////////////////////////////////////////////////////////////////////
 
     /** Update as needed the pixel value in the bitmap, so that the caller can
         access the pixels directly.
         @return The device contents as a bitmap
     */
     virtual const SkBitmap& onAccessBitmap() = 0;
 
     /**
@@ skipping 133 matching lines @@
     SkDeviceProperties* fLeakyProperties;   // will always exist.
 
 #ifdef SK_DEBUG
     bool        fAttachedToCanvas;
 #endif
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif