Track nested picture xform state for layer hoisting

src/gpu/GrPictureUtils.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 GrPictureUtils_DEFINED
 #define GrPictureUtils_DEFINED
 
@@ skipping 10 matching lines @@
         SaveLayerInfo() : fPicture(NULL), fPaint(NULL) {}
         ~SaveLayerInfo() { SkSafeUnref(fPicture); SkDELETE(fPaint); }
 
         // The picture owning the layer. If the owning picture is the top-most
         // one (i.e., the picture for which this GrAccelData was created) then
         // this pointer is NULL. If it is a nested picture then the pointer
         // is non-NULL and owns a ref on the picture.
         const SkPicture* fPicture;
         // The device space bounds of this layer.
         SkIRect fBounds;
-        // The matrix state in which this layer's draws must occur. It does not
-        // include the translation needed to map the layer's top-left point to the origin.
-        SkMatrix fOriginXform;
+        // The pre-matrix begins as the identity and accumulates the transforms
+        // of the containing SkPictures (if any). This matrix state has to be
+        // part of the initial matrix during replay so that it will be 
+        // preserved across setMatrix calls.
+        SkMatrix fPreMat;
+        // The matrix state (in the leaf picture) in which this layer's draws 
+        // must occur. It will/can be overridden by setMatrix calls in the
+        // layer itself. It does not include the translation needed to map the 
+        // layer's top-left point to the origin (which must be part of the
+        // initial matrix).
+        SkMatrix fLocalMat;
         // The paint to use on restore. Can be NULL since it is optional.
         const SkPaint* fPaint;
         // The ID of this saveLayer in the picture. 0 is an invalid ID.
         size_t  fSaveLayerOpID;
         // The ID of the matching restore in the picture. 0 is an invalid ID.
         size_t  fRestoreOpID;
         // True if this saveLayer has at least one other saveLayer nested within it.
         // False otherwise.
         bool    fHasNestedLayers;
         // True if this saveLayer is nested within another. False otherwise.
@@ skipping 20 matching lines @@
 
 private:
     SkTArray<SaveLayerInfo, true> fSaveLayerInfo;
 
     typedef SkPicture::AccelData INHERITED;
 };
 
 const GrAccelData* GPUOptimize(const SkPicture* pict);
 
 #endif // GrPictureUtils_DEFINED