Dynamically create stencil buffer when needed.

src/gpu/GrDrawTarget.h

Index: src/gpu/GrDrawTarget.h
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index e52ee6648f1c7cd433d5142148ffc63f4a2d7ff4..2da63d80ad4ec8b8bc9f3ad6cbace90b5f474f67 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -726,7 +726,7 @@ private:
     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();
         }
     }