Reorganize Layer Hoisting code

src/gpu/GrLayerHoister.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrLayerHoister_DEFINED
+#define GrLayerHoister_DEFINED
+
+#include "SkPicture.h"
+#include "SkTDArray.h"
+
+class GrAccelData;
+struct GrCachedLayer;
+struct SkRect;
+
+// This class collects the layer hoisting functionality in one place.
+// For each picture rendering:
+//  FindLayersToHoist should be called once to collect the required layers
+//  DrawLayers should be called once to render them
+//  UnlockLayers should be called once to allow the texture resources to be recycled
+class GrLayerHoister {
+public:
+    /** Find the layers in 'gpuData' that need hoisting.
+        @param gpuData  Acceleration structure containing layer information for a picture
+        @param ops      If a BBH is being used the operations about to be executed; NULL otherwise.
+        @param query    The rectangle that is about to be drawn.
+        @param pullForward A gpuData->numSaveLayers -sized Boolean array indicating 
+                           which layers are to be hoisted
+        Return true if any layers are suitable for hoisting; false otherwise
+    */
+    static bool FindLayersToHoist(const GrAccelData *gpuData,
+                                  const SkPicture::OperationList* ops,
+                                  const SkRect& query,
+                                  bool pullForward[]);
+
+    /** Draw the specified layers of 'picture' into either the atlas or free
+        floating textures.
+        @param picture  The picture containing the layers
+        @param atlased  The layers to be drawn into the atlas
+        @param nonAtlased The layers to be drawn into their own textures
+    */
+    static void DrawLayers(const SkPicture* picture,
+                           const SkTDArray<GrCachedLayer*>& atlased,
+                           const SkTDArray<GrCachedLayer*>& nonAtlased);
+
+    /** Unlock all the layers associated with picture in the layer cache.
+        @param layerCache holder of the locked layers
+        @pmara picture    the source of the locked layers
+    */
+    static void UnlockLayers(GrLayerCache* layerCache, const SkPicture* picture);
+};
+
+#endif