Add CPU backing store for GrAtlas to reduce texture uploads

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 40 matching lines @@
 
 void GrLayerCache::init() {
     static const int kAtlasTextureWidth = 1024;
     static const int kAtlasTextureHeight = 1024;
 
     SkASSERT(NULL == fAtlasMgr.get());
 
     // The layer cache only gets 1 plot
     SkISize textureSize = SkISize::Make(kAtlasTextureWidth, kAtlasTextureHeight);
     fAtlasMgr.reset(SkNEW_ARGS(GrAtlasMgr, (fGpu, kSkia8888_GrPixelConfig,
-                                            textureSize, 1, 1)));
+                                            textureSize, 1, 1, false)));
 }
 
 void GrLayerCache::freeAll() {
     fLayerHash.deleteAll();
     fAtlasMgr.free();
 }
 
 GrCachedLayer* GrLayerCache::createLayer(SkPicture* picture, int layerID) {
     GrCachedLayer* layer = fLayerPool.alloc();
 
     SkASSERT(picture->uniqueID() != SK_InvalidGenID);
     layer->init(picture->uniqueID(), layerID);
     fLayerHash.insert(PictureLayerKey(picture->uniqueID(), layerID), layer);
     return layer;
 }
 
 
 GrCachedLayer* GrLayerCache::findLayerOrCreate(SkPicture* picture, int layerID) {
     SkASSERT(picture->uniqueID() != SK_InvalidGenID);
     GrCachedLayer* layer = fLayerHash.find(PictureLayerKey(picture->uniqueID(), layerID));
     if (NULL == layer) {
         layer = this->createLayer(picture, layerID);
     }
     return layer;
 }