Add rendertarget flag to prevent a debug assert in SampleApp.

src/gpu/gl/GrGLGpu.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 "GrGLGpu.h"
 #include "GrGLGLSL.h"
@@ skipping 460 matching lines @@
             idDesc.fLifeCycle = GrGpuResource::kAdopted_LifeCycle;
             break;
         case kBorrow_GrWrapOwnership:
             idDesc.fLifeCycle = GrGpuResource::kBorrowed_LifeCycle;
             break;
     }    
     idDesc.fSampleConfig = GrRenderTarget::kUnified_SampleConfig;
 
     GrSurfaceDesc desc;
     desc.fConfig = wrapDesc.fConfig;
-    desc.fFlags = kCheckAllocation_GrSurfaceFlag;
+    desc.fFlags = kCheckAllocation_GrSurfaceFlag | kRenderTarget_GrSurfaceFlag;
     desc.fWidth = wrapDesc.fWidth;
     desc.fHeight = wrapDesc.fHeight;
     desc.fSampleCnt = SkTMin(wrapDesc.fSampleCnt, this->caps()->maxSampleCount());
     desc.fOrigin = resolve_origin(wrapDesc.fOrigin, true);
 
     GrRenderTarget* tgt = SkNEW_ARGS(GrGLRenderTarget, (this, desc, idDesc));
     if (wrapDesc.fStencilBits) {
         GrGLStencilAttachment::IDDesc sbDesc;
         GrGLStencilAttachment::Format format;
         format.fInternalFormat = GrGLStencilAttachment::kUnknownInternalFormat;
@@ skipping 2704 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }