Allow previously-hoisted layers to be reused in the same draw

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
 
@@ skipping 18 matching lines @@
         SkIPoint         fOffset;
         SkMatrix         fCTM;
     };
 
     /** Find the layers in 'topLevelPicture' that need hoisting. Note that the discovered
         layers can be inside nested sub-pictures.
         @param topLevelPicture The top-level picture that is about to be rendered
         @param query       The rectangle that is about to be drawn.
         @param atlased     Out parameter storing the layers that should be hoisted to the atlas
         @param nonAtlased  Out parameter storing the layers that should be hoisted stand alone
+        @param recycled    Out parameter storing layers that need hoisting but not rendering
         @param layerCache The source of new layers
         Return true if any layers are suitable for hoisting; false otherwise
     */
     static bool FindLayersToHoist(const SkPicture* topLevelPicture,
                                   const SkRect& query,
                                   SkTDArray<HoistedLayer>* altased,
                                   SkTDArray<HoistedLayer>* nonAtlased,
+                                  SkTDArray<HoistedLayer>* recycled,
                                   GrLayerCache* layerCache);
 
     /** Draw the specified layers into either the atlas or free floating textures.
         @param atlased      The layers to be drawn into the atlas
         @param nonAtlased   The layers to be drawn into their own textures
-        @oaram replacements The replacement structure to fill in with the rendered layer info
+        @param recycled     Layers that don't need rendering but do need to go into the 
+                            replacements object
+        @param replacements The replacement structure to fill in with the rendered layer info
     */
     static void DrawLayers(const SkTDArray<HoistedLayer>& atlased,
                            const SkTDArray<HoistedLayer>& nonAtlased,
+                           const SkTDArray<HoistedLayer>& recycled,
                            GrReplacements* replacements);
 
     /** Unlock unneeded layers in the layer cache.
         @param layerCache holder of the locked layers
         @param atlased    Unneeded layers in the atlas
         @param nonAtlased Unneeded layers in their own textures
+        @param recycled   Unneeded layers that did not require rendering
     */
     static void UnlockLayers(GrLayerCache* layerCache,
                              const SkTDArray<HoistedLayer>& atlased,
-                             const SkTDArray<HoistedLayer>& nonAtlased);
+                             const SkTDArray<HoistedLayer>& nonAtlased,
+                             const SkTDArray<HoistedLayer>& recycled);
 };
 
 #endif