Make the canvas draw looper internal layer not part of SkCanvas save count

include/core/SkDrawLooper.h

 
 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkDrawLooper_DEFINED
@@ skipping 38 matching lines @@
          *  canvas and/or paint). When false is finally returned, drawing for the object
          *  stops.
          *
          *  On each call, the paint will be in its original state, but the
          *  canvas will be as it was following the previous call to next() or
          *  createContext().
          *
          *  The implementation must ensure that, when next() finally returns
          *  false, the canvas has been restored to the state it was
          *  initially, before createContext() was first called.
+         *
+         *  It is an error to call SkCanvas::restore() or SkCanvas::restoreToCount on the canvas
+         *  from this function, unless corresponding SkCanvas::save() or SkCanvas::saveLayer() has
+         *  been called. The corresponding save call must be made from this function, but it may be
+         *  made from earlier invocation.
          */
         virtual bool next(SkCanvas* canvas, SkPaint* paint) = 0;
     };
 
     /**
      *  Called right before something is being drawn. Returns a Context
      *  whose next() method should be called until it returns false.
      *  The caller has to ensure that the storage pointer provides enough
      *  memory for the Context. The required size can be queried by calling
      *  contextSize(). It is also the caller's responsibility to destroy the
@@ skipping 43 matching lines @@
     SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper)
 
 protected:
     SkDrawLooper() {}
 
 private:
     typedef SkFlattenable INHERITED;
 };
 
 #endif