Dynamically create stencil buffer when needed.

src/gpu/GrDrawTarget.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawTarget_DEFINED
 #define GrDrawTarget_DEFINED
 
@@ skipping 708 matching lines @@
 
 private:
     /**
      * This will be called before allocating a texture as a dst for copySurface. This function
      * populates the dstDesc's config, flags, and origin so as to maximize efficiency and guarantee
      * success of the copySurface call.
      */
     void initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* dstDesc) {
         if (!this->onInitCopySurfaceDstDesc(src, dstDesc)) {
             dstDesc->fOrigin = kDefault_GrSurfaceOrigin;
-            dstDesc->fFlags = kRenderTarget_GrSurfaceFlag | kNoStencil_GrSurfaceFlag;
+            dstDesc->fFlags = kRenderTarget_GrSurfaceFlag;
             dstDesc->fConfig = src->config();
         }
     }
 
     /** Internal implementation of canCopySurface. */
     bool internalCanCopySurface(const GrSurface* dst,
                                 const GrSurface* src,
                                 const SkIRect& clippedSrcRect,
                                 const SkIPoint& clippedDstRect);
 
@@ skipping 151 matching lines @@
     virtual bool setupClip(GrPipelineBuilder*,
                            GrPipelineBuilder::AutoRestoreEffects* are,
                            GrPipelineBuilder::AutoRestoreStencil* ars,
                            GrScissorState* scissorState,
                            const SkRect* devBounds) SK_OVERRIDE;
 
     typedef GrDrawTarget INHERITED;
 };
 
 #endif