Dynamically create stencil buffer when needed.

tests/ReadPixelsTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkCanvas.h"
 #include "SkColorPriv.h"
@@ skipping 295 matching lines @@
                 GrContextFactory::GLContextType type =
                     static_cast<GrContextFactory::GLContextType>(glCtxType);
                 if (!GrContextFactory::IsRenderingGLContext(type)) {
                     continue;
                 }
                 GrContext* context = factory->get(type);
                 if (NULL == context) {
                     continue;
                 }
                 GrSurfaceDesc desc;
-                desc.fFlags = kRenderTarget_GrSurfaceFlag | kNoStencil_GrSurfaceFlag;
+                desc.fFlags = kRenderTarget_GrSurfaceFlag;
                 desc.fWidth = DEV_W;
                 desc.fHeight = DEV_H;
                 desc.fConfig = kSkia8888_GrPixelConfig;
                 desc.fOrigin = 1 == dtype ? kBottomLeft_GrSurfaceOrigin : kTopLeft_GrSurfaceOrigin;
                 SkAutoTUnref<GrTexture> texture(context->createTexture(desc, false));
                 surface.reset(SkSurface::NewRenderTargetDirect(texture->asRenderTarget()));
 #else
                 continue;
 #endif
             }
@@ skipping 56 matching lines @@
                         checkRead(reporter, wkbmp, clippedRect.fLeft,
                                   clippedRect.fTop, true, false);
                     } else {
                         REPORTER_ASSERT(reporter, !success);
                     }
                 }
             }
         }
     }
 }