Start to propagate constness of GrPipelineBuilder up the stack

src/gpu/GrGpu.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpu_DEFINED
 #define GrGpu_DEFINED
 
@@ skipping 227 matching lines @@
      * be discarded.
      **/
     virtual void discard(GrRenderTarget* = NULL) = 0;
 
     /**
      * This is can be called before allocating a texture to be a dst for copySurface. It will
      * populate the origin, config, and flags fields of the desc such that copySurface can
      * efficiently succeed. It should only succeed if it can allow copySurface to perform a copy
      * that would be more effecient than drawing the src to a dst render target.
      */
-    virtual bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) = 0;
+    virtual bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const = 0;
 
     // After the client interacts directly with the 3D context state the GrGpu
     // must resync its internal state and assumptions about 3D context state.
     // Each time this occurs the GrGpu bumps a timestamp.
     // state of the 3D context
     // At 10 resets / frame and 60fps a 64bit timestamp will overflow in about
     // a billion years.
     typedef uint64_t ResetTimestamp;
 
     // This timestamp is always older than the current timestamp
@@ skipping 214 matching lines @@
     GrTraceMarkerSet                                                    fActiveTraceMarkers;
     GrTraceMarkerSet                                                    fStoredTraceMarkers;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
     GrContext*                                                          fContext;
 
     friend class GrPathRendering;
     typedef SkRefCnt INHERITED;
 };
 
 #endif