add SkPixmap and external locking to bitmaps

include/core/SkBitmap.h

Index: include/core/SkBitmap.h
diff --git a/include/core/SkBitmap.h b/include/core/SkBitmap.h
index a39c8688ae17d2db78171a9c7757145eb54f47e6..144e93ba8864bc1ee621835f69e7d2d78387a295 100644
--- a/include/core/SkBitmap.h
+++ b/include/core/SkBitmap.h
@@ -11,6 +11,7 @@
 #include "SkColor.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
+#include "SkPixmap.h"
 #include "SkPoint.h"
 #include "SkRefCnt.h"
 
@@ -428,6 +429,8 @@ public:
      */
     bool lockPixelsAreWritable() const;
 
+    bool requestLock(SkAutoPixmapUnlock* result) const;
+
     /** Call this to be sure that the bitmap is valid enough to be drawn (i.e.
         it has non-null pixels, and if required by its colortype, it has a
         non-null colortable. Returns true if all of the above are met.