Fix layer hoisting image filter corner cases

src/core/SkLayerInfo.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 SkLayerInfo_DEFINED
 #define SkLayerInfo_DEFINED
 
@@ skipping 10 matching lines @@
         BlockInfo() : fPicture(NULL), fPaint(NULL), fKey(NULL), fKeySize(0) {}
         ~BlockInfo() { SkSafeUnref(fPicture); SkDELETE(fPaint); SkDELETE_ARRAY(fKey); }
 
         // The picture owning the layer. If the owning picture is the top-most
         // one (i.e., the picture for which this SkLayerInfo 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.
         SkRect fBounds;
+        // If not-empty, the optional bounds parameter passed in to the saveLayer
+        // call.
+        SkRect fSrcBounds;
         // 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).
@@ skipping 32 matching lines @@
     // incorporate the clip and matrix state into the key
     static SkPicture::AccelData::Key ComputeKey();
 
 private:
     SkTArray<BlockInfo, true> fBlocks;
 
     typedef SkPicture::AccelData INHERITED;
 };
 
 #endif // SkLayerInfo_DEFINED