SkDiscardablePixelRef objects are now marked immutable.

include/core/SkImageGenerator.h

Index: include/core/SkImageGenerator.h
diff --git a/include/core/SkImageGenerator.h b/include/core/SkImageGenerator.h
index e43fbc1b285891734d8a64012602e2745a9a05c2..c56e62a9d671642be8b1db78b187e2a22aea73fc 100644
--- a/include/core/SkImageGenerator.h
+++ b/include/core/SkImageGenerator.h
@@ -37,6 +37,9 @@ public:
      *  Return some information about the image, allowing the owner of
      *  this object to allocate pixels.
      *
+     *  Repeated calls to this function should give the same results,
+     *  allowing the PixelRef to be immutable.
+     *
      *  @return false if anything goes wrong.
      */
     virtual bool getInfo(SkImageInfo* info) = 0;
@@ -46,6 +49,9 @@ public:
      *  least (info.fHeight - 1) * rowBytes + (info.fWidth *
      *  bytesPerPixel)
      *
+     *  Repeated calls to this function should give the same results,
+     *  allowing the PixelRef to be immutable.
+     *
      *  @param info A description of the format (config, size)
      *         expected by the caller.  This can simply be identical
      *         to the info returned by getInfo().