Modify GrClipMaskManager to reflect logical constness

include/gpu/GrProcessorDataManager.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrProcessorDataManager_DEFINED
 #define GrProcessorDataManager_DEFINED
 
 #include "SkRefCnt.h"
 
 class GrProcessorDataManager : public SkRefCnt {
 public:
     GrProcessorDataManager() {}
     GrProcessorDataManager(const GrProcessorDataManager& procDataManager) {}
 
     void* operator new(size_t size);
     void operator delete(void* target);
 
     void* operator new(size_t size, void* placement) {
         return ::operator new(size, placement);
     }
     void operator delete(void* target, void* placement) {
         ::operator delete(target, placement);
     }
 
 private:

[robertphillips, 2015/07/10 14:34:09]

I'm not crazy about 'height' here

+    uint32_t currentHeight() const { return 0; }
+    void restoreHeight(uint32_t height) {}
+
+    // For GrPipelineBuilder::AutoRestoreProcessorDataManager
+    friend class GrPipelineBuilder;
+
     typedef SkRefCnt INHERITED;
 };
 
 #endif