There is an unused rowBytes parameter being passed along.

example/HelloWorld.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  */
 
 #include "HelloWorld.h"
@@ skipping 139 matching lines @@
 void HelloWorldWindow::draw(SkCanvas* canvas) {
     drawContents(canvas);
     // in case we have queued drawing calls
     fContext->flush();
     // Invalidate the window to force a redraw. Poor man's animation mechanism.
     this->inval(NULL);
 
     if (kRaster_DeviceType == fType) {
         // need to send the raster bits to the (gpu) window
         SkImage* snap = fSurface->newImageSnapshot();
-        size_t rowBytes;
+        size_t rowBytes = 0;
         SkImageInfo info;
         const void* pixels = snap->peekPixels(&info, &rowBytes);
         fRenderTarget->writePixels(0, 0, snap->width(), snap->height(),
                                         SkImageInfo2GrPixelConfig(info.colorType(),
                                                                 info.alphaType(),
                                                                 info.profileType()),
                                         pixels,
                                         rowBytes,
                                         GrContext::kFlushWrites_PixelOp);
         SkSafeUnref(snap);
@@ skipping 12 matching lines @@
         setUpBackend();
         this->setTitle();
         this->inval(NULL);
     }
     return true;
 }
 
 SkOSWindow* create_sk_window(void* hwnd, int , char** ) {
     return new HelloWorldWindow(hwnd);
 }