Start to propagate constness of GrPipelineBuilder up the stack

src/gpu/gl/GrGLGpu.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 GrGLGpu_DEFINED
 #define GrGLGpu_DEFINED
 
@@ skipping 52 matching lines @@
     GrPixelConfig preferredWritePixelsConfig(GrPixelConfig writeConfig,
                                              GrPixelConfig surfaceConfig) const override;
     bool canWriteTexturePixels(const GrTexture*, GrPixelConfig srcConfig) const override;
     bool readPixelsWillPayForYFlip(GrRenderTarget* renderTarget,
                                    int left, int top,
                                    int width, int height,
                                    GrPixelConfig config,
                                    size_t rowBytes) const override;
     bool fullReadPixelsIsFasterThanPartial() const override;
 
-    bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) override;
+    bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const override;
 
     // These functions should be used to bind GL objects. They track the GL state and skip redundant
     // bindings. Making the equivalent glBind calls directly will confuse the state tracking.
     void bindVertexArray(GrGLuint id) {
         fHWGeometryState.setVertexArrayID(this, id);
     }
     void bindIndexBufferAndDefaultVertexArray(GrGLuint id) {
         fHWGeometryState.setIndexBufferIDOnDefaultVertexArray(this, id);
     }
     void bindVertexBuffer(GrGLuint id) {
@@ skipping 416 matching lines @@
 
     // we record what stencil format worked last time to hopefully exit early
     // from our loop that tries stencil formats and calls check fb status.
     int fLastSuccessfulStencilFmtIdx;
 
     typedef GrGpu INHERITED;
     friend class GrGLPathRendering; // For accessing setTextureUnit.
 };
 
 #endif