make explicit the requirement that all colorfilters are reentrant-safe

include/core/SkColorFilter.h

 
 /*
  * Copyright 2006 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 SkColorFilter_DEFINED
 #define SkColorFilter_DEFINED
 
 #include "SkColor.h"
 #include "SkFlattenable.h"
 #include "SkXfermode.h"
 
 class SkBitmap;
 class GrEffectRef;
 class GrContext;
 
+/**
+ *  ColorFilters are optional objects in the drawing pipeline. When present in
+ *  a paint, they are called with the "src" colors, and return new colors, which
+ *  are then passed onto the next stage (either ImageFilter or Xfermode).
+ *
+ *  All subclasses are required to be reentrant-safe : it must be legal to share
+ *  the same instance between several threads.
+ */
 class SK_API SkColorFilter : public SkFlattenable {
 public:
     SK_DECLARE_INST_COUNT(SkColorFilter)
 
     /**
      *  If the filter can be represented by a source color plus Mode, this
      *  returns true, and sets (if not NULL) the color and mode appropriately.
      *  If not, this returns false and ignores the parameters.
      */
     virtual bool asColorMode(SkColor* color, SkXfermode::Mode* mode) const;
@@ skipping 94 matching lines @@
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 protected:
     SkColorFilter() {}
     SkColorFilter(SkFlattenableReadBuffer& rb) : INHERITED(rb) {}
 
 private:
     typedef SkFlattenable INHERITED;
 };
 
 #endif