check for null-device pixels in onWritePixels, so we don't crash

src/core/SkBitmapDevice.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkConfig8888.h"
 #include "SkDraw.h"
@@ skipping 334 matching lines @@
         }
         rect_memcpy(dstPixels, dstRowBytes, srcPixels, srcRowBytes,
                     srcInfo.width() * srcInfo.bytesPerPixel(), srcInfo.height());
     }
     // TODO: add support for more conversions as needed
     return false;
 }
 
 bool SkBitmapDevice::onWritePixels(const SkImageInfo& srcInfo, const void* srcPixels,
                                    size_t srcRowBytes, int x, int y) {
+    // since we don't stop creating un-pixeled devices yet, check for no pixels here
+    if (NULL == fBitmap.getPixels()) {
+        return false;
+    }
+
     SkImageInfo dstInfo = fBitmap.info();
     dstInfo.fWidth = srcInfo.width();
     dstInfo.fHeight = srcInfo.height();
 
     void* dstPixels = fBitmap.getAddr(x, y);
     size_t dstRowBytes = fBitmap.rowBytes();
 
     if (write_pixels(dstInfo, dstPixels, dstRowBytes, srcInfo, srcPixels, srcRowBytes)) {
         fBitmap.notifyPixelsChanged();
         return true;
@@ skipping 210 matching lines @@
         paint.getStyle() != SkPaint::kFill_Style ||
         !SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode)) {
         // turn off lcd
         flags->fFlags = paint.getFlags() & ~SkPaint::kLCDRenderText_Flag;
         flags->fHinting = paint.getHinting();
         return true;
     }
     // we're cool with the paint as is
     return false;
 }