Use variable length key (rather than accumulated matrix) as save layer hoisting key

src/gpu/GrLayerHoister.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 "GrLayerCache.h"
 #include "GrLayerHoister.h"
 #include "GrRecordReplaceDraw.h"
@@ skipping 16 matching lines @@
                                  int numSamples) {
     const SkPicture* pict = info.fPicture ? info.fPicture : topLevelPicture;
 
     SkMatrix combined = SkMatrix::Concat(info.fPreMat, info.fLocalMat);
 
     GrCachedLayer* layer = layerCache->findLayerOrCreate(pict->uniqueID(),
                                                          info.fSaveLayerOpID,
                                                          info.fRestoreOpID,
                                                          layerRect,
                                                          combined,
+                                                         info.fKey,
+                                                         info.fKeySize,
                                                          info.fPaint);
     GrSurfaceDesc desc;
     desc.fFlags = kRenderTarget_GrSurfaceFlag;
     desc.fWidth = layerRect.width();
     desc.fHeight = layerRect.height();
     desc.fConfig = kSkia8888_GrPixelConfig;
     desc.fSampleCnt = numSamples;
 
     bool locked, needsRendering;
     if (attemptToAtlas) {
@@ skipping 143 matching lines @@
     // TODO: just replace GrReplacements::ReplacementInfo with GrCachedLayer?
     for (int i = 0; i < layers.count(); ++i) {
         GrCachedLayer* layer = layers[i].fLayer;
         const SkPicture* picture = layers[i].fPicture;
 
         SkMatrix combined = SkMatrix::Concat(layers[i].fPreMat, layers[i].fLocalMat);
 
         GrReplacements::ReplacementInfo* layerInfo =
                     replacements->newReplacement(picture->uniqueID(),
                                                  layer->start(),
-                                                 combined);
+                                                 layer->key(), layer->keySize());
         layerInfo->fStop = layer->stop();
         layerInfo->fPos = layers[i].fOffset;
 
         SkBitmap bm;
         wrap_texture(layers[i].fLayer->texture(),
                      !layers[i].fLayer->isAtlased() ? layers[i].fLayer->rect().width()
                                                     : layers[i].fLayer->texture()->width(),
                      !layers[i].fLayer->isAtlased() ? layers[i].fLayer->rect().height()
                                                     : layers[i].fLayer->texture()->height(),
                      &bm);
@@ skipping 120 matching lines @@
 void GrLayerHoister::PurgeCache(GrContext* context) {
 #if !GR_CACHE_HOISTED_LAYERS
     GrLayerCache* layerCache = context->getLayerCache();
 
     // This code completely clears out the atlas. It is required when
     // caching is disabled so the atlas doesn't fill up and force more
     // free floating layers
     layerCache->purgeAll();
 #endif
 }