Make GrReducedClip's gen ID only apply to the element list

src/gpu/GrReducedClip.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrReducedClip_DEFINED
 #define GrReducedClip_DEFINED
 
 #include "SkClipStack.h"
 #include "SkTLList.h"
 
 /**
  * This class takes a clip stack and produces a reduced set of elements that are equivalent to
  * applying that full stack within a specified query rectangle.
  */
 class SK_API GrReducedClip {
 public:
     GrReducedClip(const SkClipStack& stack, const SkRect& queryBounds);
 
     /**
-     * Uniquely identifies this reduced clip.
-     */
-    int32_t genID() const { return fGenID; }
-
-    /**
      * If hasIBounds() is true, this is the bounding box within which the reduced clip is valid, and
      * the caller must not modify any pixels outside this box. Undefined if hasIBounds() is false.
      */
     const SkIRect& ibounds() const { SkASSERT(fHasIBounds); return fIBounds; }
     int left() const { return this->ibounds().left(); }
     int top() const { return this->ibounds().top(); }
     int width() const { return this->ibounds().width(); }
     int height() const { return this->ibounds().height(); }
 
     /**
      * Indicates whether ibounds() are defined. They will always be defined if the elements() are
      * nonempty.
      */
     bool hasIBounds() const { return fHasIBounds; }
 
     typedef SkTLList<SkClipStack::Element, 16> ElementList;
 
     /**
      * Populated with a minimal list of elements that implement the clip.
      */
     const ElementList& elements() const { return fElements; }
 
     /**
+     * If elements() are nonempty, uniquely identifies the list of elements within ibounds().
+     * Otherwise undefined.
+     */
+    int32_t elementsGenID() const { SkASSERT(!fElements.isEmpty()); return fElementsGenID; }
+
+    /**
      * Indicates whether antialiasing is required to process any of the clip elements.
      */
     bool requiresAA() const { return fRequiresAA; }
 
     enum class InitialState : bool {
         kAllIn,
         kAllOut
     };
 
     InitialState initialState() const { return fInitialState; }
 
 private:
-    int32_t        fGenID;
     SkIRect        fIBounds;
     bool           fHasIBounds;
     ElementList    fElements;
+    int32_t        fElementsGenID;
     bool           fRequiresAA;
     InitialState   fInitialState;
 };
 
 #endif