Make SkImage_Gpu share it's pixelref with the surface to prevent premature return to scratch pool.

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_Base.h"
 #include "SkImagePriv.h"
 #include "SkCanvas.h"
@@ skipping 54 matching lines @@
     return SkNEW_ARGS(SkCanvas, (fDevice));
 }
 
 SkSurface* SkSurface_Gpu::onNewSurface(const SkImage::Info& info) {
     GrRenderTarget* rt = fDevice->accessRenderTarget();
     int sampleCount = rt->numSamples();
     return SkSurface::NewRenderTarget(fDevice->context(), info, sampleCount);
 }
 
 SkImage* SkSurface_Gpu::onNewImageSnapshot() {
-
-    GrRenderTarget* rt = fDevice->accessRenderTarget();
-
-    return SkImage::NewTexture(rt->asTexture());
+    return SkImage::NewTexture(fDevice->accessBitmap(false));
 }
 
 void SkSurface_Gpu::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
                               const SkPaint* paint) {
     canvas->drawBitmap(fDevice->accessBitmap(false), x, y, paint);
 }
 
 // Create a new SkGpuDevice and, if necessary, copy the contents of the old
 // device into it. Note that this flushes the SkGpuDevice but
 // doesn't force an OpenGL flush.
@@ skipping 43 matching lines @@
     desc.fConfig = SkBitmapConfig2GrPixelConfig(config);
     desc.fSampleCnt = sampleCount;
 
     SkAutoTUnref<GrTexture> tex(ctx->createUncachedTexture(desc, NULL, 0));
     if (NULL == tex) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkSurface_Gpu, (ctx, tex->asRenderTarget()));
 }