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

include/core/SkDevice.h

Index: include/core/SkDevice.h
diff --git a/include/core/SkDevice.h b/include/core/SkDevice.h
index c23b2973ee27eadc4f79619817aa7898543bb501..de43d1e8b88fd5c6acfd6613299e753425930652 100644
--- a/include/core/SkDevice.h
+++ b/include/core/SkDevice.h
@@ -82,9 +82,24 @@ public:
 
     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; }
@@ -241,7 +256,6 @@ protected:
                                 const SkMatrix*, const SkPaint&);
 
     bool readPixels(const SkImageInfo&, void* dst, size_t rowBytes, int x, int y);
-    bool peekPixels(SkPixmap*);
 
     ///////////////////////////////////////////////////////////////////////////