remove unneeded preroll

src/image/SkImage_Raster.cpp

Index: src/image/SkImage_Raster.cpp
diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index 940d5323789d6c01eb6051834ae6dbb59f386897..e3ecd6875f74dd2544e8390e492dc2cf49232623 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -58,7 +58,6 @@ public:
     bool onReadPixels(const SkImageInfo&, void*, size_t, int srcX, int srcY) const SK_OVERRIDE;
     const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const SK_OVERRIDE;
     bool getROPixels(SkBitmap*) const SK_OVERRIDE;
-    void onPreroll() const SK_OVERRIDE;
 
     // exposed for SkSurface_Raster via SkNewImageFromPixelRef
     SkImage_Raster(const SkImageInfo&, SkPixelRef*, size_t rowBytes, const SkSurfaceProps*);
@@ -155,12 +154,6 @@ bool SkImage_Raster::getROPixels(SkBitmap* dst) const {
     return true;
 }
 
-void SkImage_Raster::onPreroll() const {
-    SkBitmap bm(fBitmap);
-    bm.lockPixels();
-    bm.unlockPixels();
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage* SkImage::NewRasterCopy(const SkImageInfo& info, const void* pixels, size_t rowBytes) {