Split drawing functionality out of GrContext and into new GrDrawContext

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 "GrDrawContext.h"
 #include "GrGpu.h"
 #include "GrLayerCache.h"
 #include "GrSurfacePriv.h"
 
 #ifdef SK_DEBUG
 void GrCachedLayer::validate(const GrTexture* backingTexture) const {
     SkASSERT(SK_InvalidGenID != fKey.pictureID());
 
     if (fTexture) {
         // If the layer is in some texture then it must occupy some rectangle
@@ skipping 439 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());
 
-    fContext->discardRenderTarget(fAtlas->getTexture()->asRenderTarget());
+    GrDrawContext* drawContext = fContext->drawContext();
+
+    if (drawContext) {
+        drawContext->discard(fAtlas->getTexture()->asRenderTarget());
+    }
 }
 #endif
 
 void GrLayerCache::processDeletedPictures() {
     SkTArray<SkPicture::DeletionMessage> deletedPictures;
     fPictDeletionInbox.poll(&deletedPictures);
 
     for (int i = 0; i < deletedPictures.count(); i++) {
         this->purge(deletedPictures[i].fUniqueID);
     }
@@ skipping 24 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