Add helper for creating a SkSurface from a client created texture.

src/image/SkSurface_Gpu.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSurface_Gpu.h"
 
 #include "SkCanvas.h"
@@ skipping 81 matching lines @@
 SkSurface* SkSurface::NewRenderTarget(GrContext* ctx, Budgeted budgeted, const SkImageInfo& info,
                                       int sampleCount, const SkSurfaceProps* props) {
     SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(ctx, budgeted, info, sampleCount, props,
                                                          SkGpuDevice::kNeedClear_Flag));
     if (!device) {
         return NULL;
     }
     return SkNEW_ARGS(SkSurface_Gpu, (device));
 }
 
+SkSurface* SkSurface::NewWrappedRenderTarget(GrContext* context, GrBackendTextureDesc desc,
+                                             const SkSurfaceProps* props) {
+    if (NULL == context) {
+        return NULL;
+    }
+    if (!SkToBool(desc.fFlags & kRenderTarget_GrBackendTextureFlag)) {
+        return NULL;
+    }
+    SkAutoTUnref<GrSurface> surface(context->wrapBackendTexture(desc));
+    if (!surface) {
+        return NULL;
+    }
+    SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(surface->asRenderTarget(), props,
+                                                         SkGpuDevice::kNeedClear_Flag));
+    if (!device) {
+        return NULL;
+    }
+    return SkNEW_ARGS(SkSurface_Gpu, (device));
+}
+
 #endif