Dynamically create stencil buffer when needed.

include/gpu/GrRenderTarget.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 GrRenderTarget_DEFINED
 #define GrRenderTarget_DEFINED
 
 #include "GrSurface.h"
 #include "SkRect.h"
 
 class GrStencilBuffer;
+class GrRenderTargetPriv;
 
 /**
  * GrRenderTarget represents a 2D buffer of pixels that can be rendered to.
  * A context's render target is set by setRenderTarget(). Render targets are
  * created by a createTexture with the kRenderTarget_SurfaceFlag flag.
  * Additionally, GrContext provides methods for creating GrRenderTargets
  * that wrap externally created render targets.
  */
 class GrRenderTarget : virtual public GrSurface {
 public:
@@ skipping 56 matching lines @@
     // a MSAA RT may require explicit resolving , it may auto-resolve (e.g. FBO
     // 0 in GL), or be unresolvable because the client didn't give us the
     // resolve destination.
     enum ResolveType {
         kCanResolve_ResolveType,
         kAutoResolves_ResolveType,
         kCantResolve_ResolveType,
     };
     virtual ResolveType getResolveType() const = 0;
 
-    /**
-     * GrStencilBuffer is not part of the public API.
-     */
-    GrStencilBuffer* getStencilBuffer() const { return fStencilBuffer; }
-    void setStencilBuffer(GrStencilBuffer* stencilBuffer);
+    // Provides access to functions that aren't part of the public API.
+    GrRenderTargetPriv renderTargetPriv();
+    const GrRenderTargetPriv renderTargetPriv() const;
 
 protected:
     GrRenderTarget(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc)
         : INHERITED(gpu, lifeCycle, desc)
         , fStencilBuffer(NULL) {
         fResolveRect.setLargestInverted();
     }
 
     // override of GrResource
     void onAbandon() SK_OVERRIDE;
     void onRelease() SK_OVERRIDE;
 
 private:
+    // Checked when this object is asked to attach a stencil buffer.
+    virtual bool canAttemptStencilAttachment() const = 0;
+
+    friend class GrRenderTargetPriv;
+
     GrStencilBuffer*  fStencilBuffer;
 
     SkIRect           fResolveRect;
 
     typedef GrSurface INHERITED;
 };
 
 #endif