fix empty image constructor

src/image/SkImage_Raster.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 73 matching lines @@
     SkImage_Raster(const SkBitmap& bm, const SkSurfaceProps* props, bool lockPixels = false)
         : INHERITED(bm.width(), bm.height(), bm.getGenerationID(), props)
         , fBitmap(bm) {
         if (lockPixels) {
             fBitmap.lockPixels();
         }
         SkASSERT(fBitmap.isImmutable());
     }
 
 private:
-    SkImage_Raster() : INHERITED(0, 0, fBitmap.getGenerationID(), NULL) {
+    SkImage_Raster() : INHERITED(0, 0, kNeedNewImageUniqueID, NULL) {
         fBitmap.setImmutable();
     }
 
     SkBitmap    fBitmap;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
@@ skipping 173 matching lines @@
         // pixelref since the caller might call setImmutable() themselves
         // (thus changing our state).
         if (fBitmap.isImmutable()) {
             bitmap->setInfo(fBitmap.info(), fBitmap.rowBytes());
             bitmap->setPixelRef(fBitmap.pixelRef(), fBitmap.pixelRefOrigin());
             return true;
         }
     }
     return this->INHERITED::onAsLegacyBitmap(bitmap, mode);
 }