Limit lifetime of GrDrawContext objects

src/gpu/GrLayerCache.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAtlas.h"
 #include "GrContext.h"
 #include "GrDrawContext.h"
@@ skipping 449 matching lines @@
     for (plot = fAtlas->iterInit(&iter, GrAtlas::kLRUFirst_IterOrder);
          plot;
          plot = iter.prev()) {
         SkASSERT(0 == fPlotLocks[plot->id()]);
 
         this->purgePlot(plot);
     }
 
     SkASSERT(0 == fPictureHash.count());
 
-    GrDrawContext* drawContext = fContext->drawContext();
+    SkAutoTUnref<GrDrawContext> drawContext(fContext->drawContext());
 
     if (drawContext) {
         drawContext->discard(fAtlas->getTexture()->asRenderTarget());
     }
 }
 #endif
 
 void GrLayerCache::processDeletedPictures() {
     SkTArray<SkPicture::DeletionMessage> deletedPictures;
     fPictDeletionInbox.poll(&deletedPictures);
@@ skipping 28 matching lines @@
         fileName.appendf("\\%d", layer->fKey.pictureID());
         for (int i = 0; i < layer->fKey.keySize(); ++i) {
             fileName.appendf("-%d", layer->fKey.key()[i]);
         }
         fileName.appendf(".png");
 
         layer->texture()->surfacePriv().savePixels(fileName.c_str());
     }
 }
 #endif