explicitly delete our c++ window on quit

src/views/mac/SkNSView.mm

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #import "SkNSView.h"
 #include "SkCanvas.h"
 #include "SkSurface.h"
@@ skipping 100 matching lines @@
         }
     }
 }
 
 - (void) setFrameSize:(NSSize)newSize {
     [super setFrameSize:newSize];
     [self resizeSkView:newSize];
 }
 
 - (void)dealloc {
-    delete fWind;
+    [self freeNativeWind];
     self.fGLContext = nil;
     self.fTitle = nil;
     [super dealloc];
 }
 
+- (void)freeNativeWind {
+    delete fWind;
+    fWind = nil;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 - (void)drawSkia {
     fRedrawRequestPending = false;
     if (fWind) {
         SkAutoTUnref<SkSurface> surface(fWind->createSurface());
         fWind->draw(surface->getCanvas());
 #ifdef FORCE_REDRAW
         fWind->inval(NULL);
 #endif
@@ skipping 271 matching lines @@
     [fGLContext release];
     fGLContext = nil;
 }
 
 - (void)present {
     if (nil != fGLContext) {
         [fGLContext flushBuffer];
     }
 }
 @end