Address MSAA rendering in layer hoisting

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 "GrGpu.h"
 #include "GrLayerCache.h"
@@ skipping 146 matching lines @@
 
     return layer;
 }
 
 bool GrLayerCache::tryToAtlas(GrCachedLayer* layer, 
                               const GrSurfaceDesc& desc, 
                               bool* needsRendering) {
     SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas ? fAtlas->getTexture() : NULL, layer);)
 
     SkASSERT(PlausiblyAtlasable(desc.fWidth, desc.fHeight));
+    SkASSERT(0 == desc.fSampleCnt);
 
     if (layer->locked()) {
         // This layer is already locked
         SkASSERT(fAtlas);
         SkASSERT(layer->isAtlased());
         SkASSERT(layer->rect().width() == desc.fWidth);
         SkASSERT(layer->rect().height() == desc.fHeight);
         *needsRendering = false;
         return true;
     }
@@ skipping 323 matching lines @@
             continue;
         }
 
         SkString fileName(dirName);
         fileName.appendf("\\%d-%d.png", layer->fKey.pictureID(), layer->fKey.start());
 
         layer->texture()->surfacePriv().savePixels(fileName.c_str());
     }
 }
 #endif